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《Java语言程序设计(基础篇)》(第10版 梁勇 著)第九章练习题答案

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java语言程序设计基础篇第十版课后答案

java语言程序设计基础篇第十版课后答案

第一章1.1public class Test{public static void main(String[]args){System.out.println("Welcome to Java!"); System.out.println("Welcome to Computer Science!");System.out.println("Progr amming is fun.");}}1.2public class Test{public static void main(String[]args){for(int i=0;i<=4;i++){System.out.println("Welcome to Java!");}}}1.3public class Test{public static void main(String[]args){System.out.println("]");System.out.printl n("]");System.out.println("]]");System.out.println("]]");}}public class Test{public static void main(String[]args){System.out.println("A"); System.out.println("A A");System.out.println("AAAAA");System.out.println("A A");}}public class Test{public static void main(String[]args){System.out.println("V V");System.out.println("V V");System.out.println("V V");System.out.println(" V");}}1.4public class Test{public static void main(String[]args){System.out.println("a a^2a^3");System.out.println("111");System.out.println("248");System.out.println("3 927");System.out.println("41664");}}1.5public class Test{public static void main(String[]args){System.out.println((9.5*4.5-2.5*3)/(45.5-3.5) );}}1.6public class Test{public static void main(String[]args){int i=1,sum=0;for(;i<=9;i++)sum+ =i;System.out.println(sum);}1.7public class Test{public static void main(String[]args){System.out.println(4*(1.0-1.0/3+1.0/5-1.0/7+1.0/9-1.0/11));System.out.println(4*(1.0-1.0/3+1.0/5-1.0/7+1.0/9-1.0/11+1.0/13));}}1.8public class Test{public static void main(String[]args){final double PI=3.14; double radius=5.5;System.out.println(2*radius*PI);System.out.println(PI*radius*radius);}}1.9public class Test{public static void main(String[]args){System.out.println(7.9*4.5);System.out.p rintln(2*(7.9+4.5));}}1.10public class Test{public static void main(String[]args){double S=14/1.6;double T=45*60+30;double speed=S/T;System.out.println(speed);}1.11public class Test{public static void main(String[]args){int BN=312032486; //original person numbers double EveryYS,EveryYBP,EveryYDP,EveryYMP;EveryY S=365*24*60*60;EveryYBP=EveryYS/7;EveryYDP=EveryYS/13;Every YMP=EveryYS/45;int FirstYP,SecondYP,ThirdYP,FourthYP,FivthYP;FirstYP=(int)(BN+EveryYBP+EveryYMP-EveryYDP);SecondYP=(int)(FirstYP +EveryYBP+EveryYMP-EveryYDP);ThirdYP=(int)(SecondYP+EveryYBP+Ev eryYMP-EveryYDP);FourthYP=(int)(ThirdYP+EveryYBP+EveryYMP-EveryYD P);FivthYP=(int)(FourthYP+EveryYBP+EveryYMP-EveryYDP);System.out.pri ntln(FirstYP);System.out.println(SecondYP);System.out.println(ThirdYP);Syste m.out.println(FourthYP);System.out.println(FivthYP);}}1.12public class Test{public static void main(String[]args){double S=24*1.6; double T=(1*60+40)*60+35;double speed=S/T;System.out.println(sp eed);}}1.13import java.util.Scanner;public class Test{public static void main(String[]args){Scanner input=new Scan ner(System.in);System.out.println("input a,b,c,d,e,f value please:");double a=input.nextDouble();double b=input.nextDouble();double c=input.nextDouble();double d=input. nextDouble();double e=input.nextDouble();第二章package cn.Testcx;import java.util.Scanner;public class lesson2{public static void main(String[]args){@SuppressWarnings("resource")Scanner in put=new Scanner(System.in);System.out.print("请输入一个摄氏温度：");double Celsius=input.nextDouble();double Fahrenheit=(9.0/5)*Celsius+3 2;System.out.println("摄氏温度："+Celsius+"度"+"转换成华氏温度为："+Fahrenheit+"度");System.out.print("请输入圆柱的半径和高：");double radius=input.nextDouble();int higth=input.nextInt();double are as=radius*radius*Math.PI;double volume=areas*higth;System.out.println("圆柱体的面积为："+areas);System.out.println("圆柱体的体积为："+volume);System.out.print("输入英尺数：");double feet=input.nextDouble();double meters=feet*0.305;System.out.print ln(feet+"英尺转换成米："+meters);System.out.print("输入一个磅数：");double pounds=input.nextDouble();double kilograms=pounds*0.454;Syste m.out.println(pounds+"磅转换成千克为："+kilograms);System.out.println("输入分钟数：");long minutes=input.nextInt();long years=minutes/(24*60*365);long days=(minutes%(24*60*365))/(24*60);System.out.println(minutes+"分钟"+"有"+years+"年和"+days+"天");long totalCurrentTimeMillis=System.currentTimeMillis();long totalSeconds=t otalCurrentTimeMillis/1000;long currentSeconds=totalSeconds%60;long totalM inutes=totalSeconds/60;long currentMinutes=(totalSeconds%(60*60))/60;long currenthours=(totalMinutes/60)%24;System.out.print("输入时区偏移量：");byte zoneOffset=input.nextByte();long currentHour=(currenthours+(zoneOf fset*1))%24;System.out.println("当期时区的时间为："+currentHour+"时"+currentMinutes+"分"+currentSeconds+"秒");System.out.print("请输入v0,v1,t:");double v0=input.nextDouble();double v1=input.nextDouble();doublet=input.nextDouble();float a=(float)((v1-v0)/t);System.out.println("平均加速度a="+a);System.out.println("输入水的重量、初始温度、最终温度：");double water=input.nextDouble();double initialTemperature=input.nextDou ble();double finalTemperature=input.nextDouble();double Q=water*(finalTemp erature-initialTemperature)*4184;System.out.println("所需热量为："+Q);System.out.print("输入年数：");int numbers=input.nextInt();long oneYearsSecond=365*24*60*60;Longpop ulation=(long)((312032486+((oneYearsSecond/7.0)+(oneYearsSecond/45.0)-(oneYearsSecond/13.0))*numbers));System.out.println("第"+numbers+"年后人口总数为："+population);System.out.print("输入速度单位m/s和加速度a单位m/s2:");double v=input.nextDouble();double a1=input.nextDouble();double l engthOfAirplane=(Math.pow(v,2))/(2*a1);System.out.println("最短长度为："+lengthOfAirplane);System.out.print("输入存入的钱：");double money=input.nextInt();double monthRate=5.0/1200;for(int i=1;i<7; i++){double total=money*(Math.pow(1+monthRate,i));System.out.println("第"+i+"个月的钱为："+total);//告诉我书上的银行在哪里，我要去存钱，半年本金直接翻6倍、、、}System.out.print("用户请输入身高(英寸)、体重(磅):");double height=input.nextDouble();double weight=input.nextDouble(); double BMI=(weight*0.45359237)/(Math.pow((height*0.0254),2));System.out.println("BMI的值为"+BMI);System.out.print("输入x1和y1:");System.out.print("输入x2和y2:");double x1=input.nextDouble();double y1=input.nextDouble();double x2 =input.nextDouble();double y2=input.nextDouble();double point1=Math.pow((x2-x1),2);double point2=Math.pow((y2-y1),2);double distance=Math.pow((point1+point2),(1.0/2));//也可以Math.pow((point1+point2),0.5)System.out.println("两点间的距离为："+distance);System.out.print("输入六边形的边长：");double side=input.nextDouble();double area=(3*(Math.pow(3,0.5))*(Math.p ow(side,2)))/2;System.out.println("六边形的面积为："+area);}}。

java语言程序设计方案课后习题答案

java语言程序设计方案课后习题答案

习题23．使用“= =”对相同内容的字符串进行比较，看会产生什么样的结果。

答：首先创建一个字符串变量有两种方式：String str = new String("abc")。

String str = "abc"；使用“= =”会因为创建的形式不同而产生不同的结果：String str1 = "abc"。

String str2 = "abc"。

System.out.println(str1==str2)。

//trueString str1 = new String("abc")。

String str2 = "abc"。

System.out.println(str1==str2)。

//falseString str1 = new String("abc")。

String str2 = new String("abc")。

System.out.println(str1==str2)。

//false因此自符串如果是对内容进行比较，使用equals方法比较可靠。

String str1 = "abc"。

String str2 = "abc"。

System.out.println(str1==str2)。

//trueString str1 = new String("abc")。

String str2 = "abc"。

System.out.println(str1.equals(str2))。

//trueString str1 = new String("abc")。

String str2 = new String("abc")。

Java语言程序设计基础篇(第10版) 梁勇 课后习题答案

Java语言程序设计基础篇(第10版) 梁勇 课后习题答案

System.out.println("Programming is fun .");
}
}
1.2 public class Test{
public static void main(String[] args){
for(int i = 0;i <= 4;i++){
System.out.println("Welcome to Java !");
public static void main(String[] args){ double S = 14 / 1.6;
double T = 45 * 60 + 30; double speed = S / T; System.out.println(speed); } } 1.11 public class Test{ public static void main(String[] args){ int BN = 312032486; //original person numbers double EveryYS,EveryYBP,EveryYDP,EveryYMP; EveryYS = 365 * 24 * 60 * 60; EveryYBP = EveryYS / 7; EveryYDP = EveryYS / 13; EveryYMP = EveryYS / 45; int FirstYP,SecondYP,ThirdYP,FourthYP,FivthYP; FirstYP = (int)(BN + EveryYBP + EveryYMP - EveryYDP); SecondYP = (int)(FirstYP + EveryYBP + EveryYMP - EveryYDP); ThirdYP = (int)(SecondYP + EveryYBP + EveryYMP - EveryYDP); FourthYP = (int)(ThirdYP + EveryYBP + EveryYMP - EveryYDP); FivthYP = (int)(FourthYP + EveryYBP + EveryYMP - EveryYDP); System.out.println(FirstYP); System.out.println(SecondYP); System.out.println(ThirdYP); System.out.println(FourthYP); System.out.println(FivthYP); } } 1.12 public class Test{ public static void main(String[] args){ double S = 24 * 1.6; double T = (1 * 60 + 40) * 60 + 35; double speed = S / T; System.out.println(speed); } } 1.13 import java.util.Scanner; public class Test{ public static void main(String[] args){ Scanner input = new Scanner(System.in); System.out.println("input a,b,c,d,e,f value please:"); double a = input.nextDouble(); double b = input.nextDouble(); double c = input.nextDouble(); double d = input.nextDouble(); double e = input.nextDouble();

《Java基础入门》_课后习题答案大一计算机专业9

《Java基础入门》_课后习题答案大一计算机专业9

《Java基础入门》课后习题答案第9章JDBC一、填空题1、Java Database Connectivity2、java.sql.*3、classpath4、registerDriver()5、next()二、判断题1、对2、错3、对4、错5、错三、选择题1、A2、C3、A4、D5、AC四、简答题1、JDBC是一套用于执行SQL语句的Java API。

应用程序可通过这套API连接到关系型数据库，并使用SQL语句来完成对数据库中数据的查询、新增、更新和删除等操作。

2、（1）加载数据库驱动（2）通过DriverManager获取数据库连接（3）通过Connection对象获取Statement对象（4）使用Statement执行SQL语句（5）操作ResultSet结果集（6）关闭连接，释放资源3、（1）代码的可读性和可维护性（2）PreparedStatement尽最大可能提高性能，因为预编译语句有可能被重复调用,所以语句在被DB 的编译器编译后的执行代码被缓存下来,那么下次调用时只要是相同的预编译语句就不需要编译,只要将参数直接传入编译过的语句执行代码中（相当于一个函数）就会得到执行。

（3）极大地提高了安全性传。

递给PreparedStatement对象的参数可以被强制进行类型转换，使开发人员可以确保在插入或查询数据时与底层的数据库格式匹配；在公共Web站点环境下，防止Sq注入问题。

五、编程题1、参考答案public static void main(String[] args) throws Exception {// int i = insert();// int i = delete();// int i = update();select();// System.out.println(i);}// 获取连接对象private static Connection getConn() {String driver = "com.mysql.jdbc.Driver";String url = "jdbc:mysql://localhost:3306/javatest";String username = "root";String password = "1234";Connection conn = null;try {Class.forName(driver); // classLoader,加载对应驱动conn = DriverManager.getConnection(url, username, password);} catch (ClassNotFoundException e) {e.printStackTrace();} catch (SQLException e) {e.printStackTrace();}return conn;}// 插入操作private static int insert() {Connection conn = getConn();int i = 0;String sql = "insert into tb_user(name,sex,email,birthday) values(?,?,?,?)";PreparedStatement pstmt;try {pstmt = conn.prepareStatement(sql);pstmt.setString(1, "itcast");pstmt.setString(2, "男");pstmt.setString(3, "itcast@");pstmt.setString(4, "2000-01-01");i = pstmt.executeUpdate();pstmt.close();conn.close();} catch (SQLException e) {e.printStackTrace();}return i;}// 删除操作private static int delete() {Connection conn = getConn();int i = 0;String sql = "delete from tb_user where name=?";PreparedStatement pstmt;try {pstmt = conn.prepareStatement(sql);pstmt.setString(1, "itcast");i = pstmt.executeUpdate();} catch (Exception e) {e.printStackTrace();}return i;}// 更新操作private static int update() {Connection conn = getConn();int i = 0;String sql = "update tb_user set name=? where name =?";PreparedStatement pstmt;try {pstmt = conn.prepareStatement(sql);pstmt.setString(1, "itcast");pstmt.setString(2, "abc");i = pstmt.executeUpdate();System.out.println("resutl: " + i);pstmt.close();conn.close();} catch (SQLException e) {e.printStackTrace();}return i;}// 查询操作private static void select() {Connection conn = getConn();String sql = "select * from tb_user";PreparedStatement pstmt;try {pstmt = conn.prepareStatement(sql);ResultSet rs = pstmt.executeQuery();while (rs.next()) {int id = rs.getInt("id"); // 通过列名获取指定字段的值String name = rs.getString("name");String sex = rs.getString("sex");String email = rs.getString("email");Date birthday = rs.getDate("birthday");System.out.println(id + " | " + name + " | " + sex + " | " + email + " | " + birthday);}pstmt.close();conn.close();} catch (Exception e) {e.printStackTrace();}}2、参考答案import java.sql.*;public class Test {public static void main(String[] args) throws Exception {transferAccounts(2, 1, 100);}public static void transferAccounts(int fromid,int toid,int transferMoney) throwsException{ Class.forName("com.mysql.jdbc.Driver");String url = "jdbc:mysql://localhost:3306/jdbc";Connection con = DriverManager.getConnection(url,"root", "root");int fromMoney = getMoney(fromid);// 转出账户String sql = "update tb_count set money=? where id =?";PreparedStatement ps = con.prepareStatement(sql);ps.setInt(1, fromMoney-transferMoney);ps.setInt(2, fromid);// 转入账户int toMoney = getMoney(toid);String sql2 = "update tb_count set money=? where id =?";PreparedStatement ps2 = con.prepareStatement(sql2);ps2.setInt(1, toMoney+transferMoney);ps2.setInt(2, toid);ps.executeUpdate();ps2.executeUpdate();ps.close();ps2.close();con.close();}// 获取当前账户id的账户余额public static int getMoney(int id) throws Exception{Class.forName("com.mysql.jdbc.Driver");String url = "jdbc:mysql://localhost:3306/jdbc";Connection con = DriverManager.getConnection(url,"root", "root");String sql = "select money from tb_count where id =?";PreparedStatement ps = con.prepareStatement(sql);ps.setInt(1, id);ResultSet resultSet = ps.executeQuery();int money = 0;while(resultSet.next()){money = resultSet.getInt(1);}ps.close();con.close();return money;}}。

Java语言程序设计（基础篇）第10版习题答案Chapter9-1

Java语言程序设计（基础篇）第10版习题答案Chapter9-1

Java语⾔程序设计（基础篇）第10版习题答案Chapter9-1（矩形类 Rectangle）遵照9.2节中 Circle 类的例⼦，设计⼀个名为 Rectangle 的类表⽰矩形。

这个类包括：两个名为 width 和 height 的 double 型数据域，它们分别表⽰矩形的宽和⾼。

width 和 height 的默认值都为1。

创建默认矩形的⽆参构造⽅法⼀个创建 width 和 height 为指定值的矩形的构造⽅法。

⼀个名为 getArea() 的⽅法返回这个矩形的⾯积。

⼀个名为 getPerimeter() 的⽅法返回周长。

画出该矩形的 UML 图并实现这个类。

编写⼀个测试程序，创建两个 Rectangle 对象——⼀个矩形的宽为 4 ⽽⾼为 40，另⼀个矩形的宽为3.5 ⽽⾼为 35.9 。

按照这个顺序显⽰每个矩形的宽、⾼、⾯积、周长。

程序代码：public class Rectangle {private double width;private double height;public Rectangle(){width=1.0;height=1.0;}public Rectangle(double width,double height) {this.width=width;this.height=height;}public double getWidth() {return width;}public double getHeight() {return height;}public double getArea() {return width*height;}public double getPerimeter() {return 2*(width+height);}public static void main(String[] args) {// TODO Auto-generated method stubRectangle t1=new Rectangle(4,40);Rectangle t2=new Rectangle(3.5,35.9);System.out.println("width:"+t1.getWidth()+" height:"+t1.getHeight()+" Area:"+t1.getArea()+" Per:"+t1.getPerimeter());System.out.println("width:"+t2.getWidth()+" height:"+t2.getHeight()+" Area:"+t2.getArea()+" Per:"+t2.getPerimeter());}}运⾏结果：width:4.0 height:40.0 Area:160.0 Per:88.0width:3.5 height:35.9 Area:125.64999999999999 Per:78.8。

java语言程序设计基础篇第十版练习答案精编

java语言程序设计基础篇第十版练习答案精编

j a v a语言程序设计基础篇第十版练习答案精编Document number：WTT-LKK-GBB-08921-EIGG-2298601import class Exercise14_01 extendsApplication {@Override Not needed for running from the command line.*/public static void main(String[] args) {launch(args);}}02import class Exercise14_02 extends Application {@Override Not needed for running from the command line.*/public static void main(String[] args) {launch(args);}}03import class Exercise14_03 extends Application {@Override One is to use the hint in the book.ArrayList<Integer> list = new ArrayList<>(); for (int i = 1; i <= 52; i++) {(i);}HBox pane = new HBox(5);;().add(new ImageView("image/card/" + (0) +".png"));().add(new ImageView("image/card/" + (1) +".png"));().add(new ImageView("image/card/" + (2) +".png"));Not needed for running from the command line.*/public static void main(String[] args) {launch(args);}}04import class Exercise14_04 extends Application {@Override dd(txt);}Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}05import class Exercise14_05 extends Application {@Override dd(txt);}Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}05import class Exercise14_05 extends Application {@Override dd(txt);}Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}06import class Exercise14_06 extends Application {@Override dd(rectangle);}}Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}07import class Exercise14_07 extends Application {@Override Not needed for running from the command line.*/public static void main(String[] args) {launch(args);}}08import class Exercise14_08 extends Application {@Override ng"), j, i);}}Not needed for running from the command line.*/public static void main(String[] args) {launch(args);}}09import class Exercise14_09 extends Application {@Override Not needed for running from the command line.*/public static void main(String[] args) {launch(args);}}class FanPane extends Pane {double radius = 50;public FanPane() {Circle circle = new Circle(60, 60, radius);;;getChildren().add(circle);Arc arc1 = new Arc(60, 60, 40, 40, 30, 35);; ddAll(arc1, arc2, arc3, arc4);}}10import class Exercise14_10 extends Application {@Override ddAll, ;Arc arc2 = new Arc(100, 140, 50, 20, 180, 180); ;;().addAll(ellipse, arc1, arc2,new Line(50, 40, 50, 140), new Line(150, 40, 150, 140));Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}11import class Exercise14_11 extends Application {@Override ddAll(circle, ellipse1, ellipse2,circle1, circle2, line1, line2, line3, arc);Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}12import class Exercise14_12 extends Application {@Override ddAll(r1, text1, r2, text2, r3, text3, r4, text4);Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}13import class Exercise14_13 extends Application {@Override ddAll(arc1, text1, arc2, text2, arc3, text3, arc4, text4);Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}14import class Exercise14_14 extends Application {@Override ddAll(r1, r2, line1, line2, line3, line4);Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}15import class Exercise14_15 extends Application {@Override ddAll(polygon, text);Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}16import class Exercise14_16 extends Application {@Override ind().divide(3));().bind());().bind().divide(3));;Line line2 = new Line(0, 0, 0, 0);().bind().multiply(2).divide(3));().bind());().bind().multiply(2).divide(3));;Line line3 = new Line(0, 0, 0, 0);().bind().divide(3));().bind().divide(3));().bind());;Line line4 = new Line(0, 0, 0, 0);().bind().multiply(2).divide(3));().bind().multiply(2).divide(3));().bind());;().addAll(line1, line2, line3, line4);Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}17import class Exercise14_17 extends Application {@Override ddAll(arc, line1, line2, line3, circle, line4, line5, line6, line7, line8);Not needed for running from the command line.*/public static void main(String[] args) {launch(args);}}18import class Exercise14_18 extends Application {@Override ddAll(polyline, line1, line2,line3, line4, line5, line6, text1, text2);Not needed for running from the command line.*/public static void main(String[] args) {launch(args);}}19import class Exercise14_19 extends Application {@Override ddAll(polyline1, polyline2, line1,line2,line3, line4, line5, line6, text1, text2,text3,text4, text5, text6, text7);Not needed for running from the command line.*/public static void main(String[] args) {launch(args);}}20import class Exercise14_20 extends Application {@Override dd(new Line(x1, y1, x2, y2));dd(new Line(x2, y2, (x2 + (arctan + set45) * arrlen)),((y2)) + (arctan + set45) * arrlen)));().add(new Line(x2, y2, (x2 + (arctan - set45) * arrlen)),((y2)) + (arctan - set45) * arrlen)));}/*** The main method is only needed for the IDE with limited* JavaFX support. Not needed for running from the command line.*/public static void main(String[] args) {launch(args);}}21import class Exercise14_21 extends Application {@Override istance(x2, y2) + "");().addAll(circle1, circle2, line, text);Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}22import class Exercise14_22 extends Application {@Override ddAll(circle1, circle2, line, text1, text2);Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}23import class Exercise14_23 extends Application {@Override ddAll(r1, r2, text);Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}24import class Exercise14_24 extends Application {@Override ddAll(polygon, new Circle(x5, y5, 10), text);Not needed for running from the command line. */public static void main(String[] args) {launch(args);}25import class Exercise14_25 extends Application {@Override ddAll(circle, polygon);Not needed for running from the command line. */public static void main(String[] args) {launch(args);}}26import class Exercise14_26 extends Application {@Override ddAll(clock1, clock2);Not needed for running from the command line. */public static void main(String[] args) {launch(args);}27import class Exercise14_27 extends Application {@OverrideNot needed for running from the command line. */public static void main(String[] args) {launch(args);}}class DetailedClockPane extends Pane {private int hour;private int minute;private int second;lear();getChildren().addAll(circle, sLine, mLine, hLine);dd(new Line(xOuter, yOuter, xInner, yInner));}dd(text);}}}28import class Exercise14_28 extends Application {@OverrideNot needed for running from the command line.*/public static void main(String[] args) {launch(args);}}class ClockPaneWithBooleanProperties extends Pane { private int hour;private int minute;private int second;private boolean hourHandVisible = true;private boolean minuteHandVisible = true; private boolean secondHandVisible = true;public boolean isHourHandVisible() {return hourHandVisible;}public void setHourHandVisible(boolean hourHandVisible) {= hourHandVisible;paintClock();}public boolean isMinuteHandVisible() {return minuteHandVisible;}public void setMinuteHandVisible(boolean minuteHandVisible) {= minuteHandVisible;paintClock();}public boolean isSecondHandVisible() {return secondHandVisible;public void setSecondHandVisible(boolean secondHandVisible) {= secondHandVisible;paintClock();}lear();getChildren().addAll(circle, t1, t2, t3, t4);if (secondHandVisible) {getChildren().add(sLine);}if (minuteHandVisible) {getChildren().add(mLine);}if (hourHandVisible) {getChildren().add(hLine);}}}import class Exercise14_29 extends Application {final static double HGAP = 20;final static double VGAP = 20;final static double RADIUS = 5;final static double LENGTH_OF_SLOTS = 40;final static double LENGTH_OF_OPENNING = 15;final static double Y_FOR_FIRST_NAIL = 50;final static double NUMBER_OF_SLOTS = 9;final static double NUMBER_OF_ROWS =NUMBER_OF_SLOTS - 2;@Override dd(c);}}dd(new Line(x, y, x, y + LENGTH_OF_SLOTS)); }dd(new Line(centerX - (NUMBER_OF_ROWS - 1) * HGAP / 2 - HGAP,y + LENGTH_OF_SLOTS, centerX -(NUMBER_OF_ROWS - 1) * HGAP / 2 + NUMBER_OF_ROWS * HGAP,y + LENGTH_OF_SLOTS));dd(new Line(centerX + HGAP / 2,Y_FOR_FIRST_NAIL + RADIUS,centerX - (NUMBER_OF_ROWS - 1) * HGAP / 2 + NUMBER_OF_ROWS * HGAP, y));().add(new Line(centerX - HGAP / 2,Y_FOR_FIRST_NAIL + RADIUS,centerX - (NUMBER_OF_ROWS - 1) * HGAP / 2 - HGAP, y));dd(new Line(centerX - HGAP / 2,Y_FOR_FIRST_NAIL + RADIUS,centerX - HGAP / 2, Y_FOR_FIRST_NAIL - LENGTH_OF_OPENNING));().add(new Line(centerX + HGAP / 2,Y_FOR_FIRST_NAIL + RADIUS,centerX + HGAP / 2, Y_FOR_FIRST_NAIL - LENGTH_OF_OPENNING));Not needed for running from the command line.*/public static void main(String[] args) { launch(args);}}。

JAVA第9章第10章课后习题答案

JAVA第9章第10章课后习题答案

第9章多线程4、C5、D6、package cn.ntu.zhanbin;public class ThreadOutput implements Runnable {static ThreadOutput to = new ThreadOutput();public static void main(String[] args) {//创建两个线程Thread t1 = new Thread(new ThreadOutput());Thread t2 = new Thread(new ThreadOutput());t1.start();t2.start();}public void run() {synchronized (to) {to.print();}}void print() {for (int i = 0; i < 6; i++) {System.out.print(10 + i);if (i < 5) {System.out.print(",");}try {Thread.sleep(500);} catch (InterruptedException e) {e.printStackTrace();}}System.out.println("");}}--------------------------------------------------------------------- 8、package cn.ntu.zhanbin;public class ThreadAlphabet extends Thread {public static void main(String[] args) {//创建3个线程ThreadAlphabet ta1 = new ThreadAlphabet("线程1:");ThreadAlphabet ta2 = new ThreadAlphabet("线程2:");ThreadAlphabet ta3 = new ThreadAlphabet("线程3:");ta1.start();ta2.start();ta3.start();}ThreadAlphabet(String name) {super(name);//调用父类的构造函数}public void run() {//获取当前线程名String name = Thread.currentThread().getName();//输出for (int i = 0; i < 26; i++) {System.out.println(name + (char) (i + 65));try {Thread.sleep(200);} catch (InterruptedException e) {e.printStackTrace();}}}}--------------------------------------------------------------------- 9、package cn.ntu.zhanbin;public class PrintOdds implements Runnable {private int bound;//创建一个静态PrintOdds对象，并设置边界范围为20static PrintOdds po = new PrintOdds(20);public PrintOdds(int b) {bound = b;}public void print() {for (int i = 1; i < bound; i+=2) {System.out.println(i);}}public void run() {po.print();}public static void main(String[] args) {Thread t = new Thread(po);t.start();}}第10章数据库编程说明：课本中连接数据库和关闭数据库的操作都是调用的P201的例10-1的ConnectionManager，而书中的类只写了getConnection（）方法，各个关闭操作的方法均未给出。

java习题及答案第9章 习题参考答案

java习题及答案第9章 习题参考答案

第9章习题解答1.与输入/输出有关的流类有哪些？答：与输入/输出有关的流类主要有InputStream、OutputStream和Reader、Writer类及其子类。

除此以外，与流有关的类还有File类、FileDescriptor类、StreamTokenizer类和RandomAccessFile类。

2.字节流与字符流之间有哪些区别？答：字节流是面向字节的流，流中的数据以8位字节为单位进行读写，是抽象类InputStream和OutputStream的子类，通常用于读写二进制数据，如图像和声音。

字符流是面向字符的流，流中的数据以16位字符(Unicode字符)为单位进行读写，是抽象类Reader和Writer的子类，通常用于字符数据的处理。

3.什么是节点流？什么是处理流或过滤流？分别在什么场合使用？答：一个流有两个端点。

一个端点是程序；另一个端点可以是特定的外部设备(如键盘、显示器、已连接的网络等)和磁盘文件，甚至是一块内存区域(统称为节点)，也可以是一个已存在流的目的端。

流的一端是程序，另一端是节点的流，称为节点流。

节点流是一种最基本的流。

以其它已经存在的流作为一个端点的流，称为处理流。

处理流又称过滤流，是对已存在的节点流或其它处理流的进一步处理。

对节点流中的数据只能按字节或字符读写。

当读写的数据不是单个字节或字符，而是一个数据块或字符串等时，就要使用处理流或过滤流。

4.标准流对象有哪些？它们是哪个类的对象？答：标准流对象有3个，它们是：System.in、System.out和System.err。

System.in 是InputStream类对象，System.out和System.err是PrintStream类对象。

5.顺序读写与随机读写的特点分别是什么？答：所谓顺序读写是指在读写流中的数据时只能按顺序进行。

换言之，在读取流中的第n个字节或字符时，必须已经读取了流中的前n-1个字节或字符；同样，在写入了流中n-1个字节或字符后，才能写入第n个字节或字符。

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《Java语言程序设计（基础篇）》（第10版梁勇著）第九章练习题答案9.1public class Exercise09_01 {public static void main(String[] args) {MyRectangle myRectangle = new MyRectangle(4, 40);System.out.println("The area of a rectangle with width " +myRectangle.width + " and height " +myRectangle.height + " is " +myRectangle.getArea());System.out.println("The perimeter of a rectangle is " +myRectangle.getPerimeter());MyRectangle yourRectangle = new MyRectangle(3.5, 35.9);System.out.println("The area of a rectangle with width " +yourRectangle.width + " and height " +yourRectangle.height + " is " +yourRectangle.getArea());System.out.println("The perimeter of a rectangle is " +yourRectangle.getPerimeter());}}class MyRectangle {// Data membersdouble width = 1, height = 1;// Constructorpublic MyRectangle() {}// Constructorpublic MyRectangle(double newWidth, double newHeight) {width = newWidth;height = newHeight;}public double getArea() {return width * height;}public double getPerimeter() {return 2 * (width + height);}}9.2public class Exercise09_02 {public static void main(String[] args) {Stock stock = new Stock("SUNW", "Sun MicroSystems Inc."); stock.setPreviousClosingPrice(100);// Set current pricestock.setCurrentPrice(90);// Display stock infoSystem.out.println("Previous Closing Price: " +stock.getPreviousClosingPrice());System.out.println("Current Price: " +stock.getCurrentPrice());System.out.println("Price Change: " +stock.getChangePercent() * 100 + "%");}}class Stock {String symbol;String name;double previousClosingPrice;double currentPrice;public Stock() {}public Stock(String newSymbol, String newName) {symbol = newSymbol;name = newName;}public double getChangePercent() {return (currentPrice - previousClosingPrice) /previousClosingPrice;}public double getPreviousClosingPrice() {return previousClosingPrice;}public double getCurrentPrice() {return currentPrice;}public void setCurrentPrice(double newCurrentPrice) {currentPrice = newCurrentPrice;}public void setPreviousClosingPrice(double newPreviousClosingPrice) { previousClosingPrice = newPreviousClosingPrice;}}9.3public class Exercise09_03 {public static void main(String[] args) {Date date = new Date();int count = 1;long time = 10000;while (count <= 8) {date.setTime(time);System.out.println(date.toString());count++;time *= 10;}}}9.4public class Exercise09_04 {public static void main(String[] args) {Random random = new Random(1000);for (int i = 0; i < 50; i++)System.out.print(random.nextInt(100) + " ");}9.5public class Exercise09_05 {public static void main(String[] args) {GregorianCalendar calendar = new GregorianCalendar();System.out.println("Year is " + calendar.get(GregorianCalendar.YEAR)); System.out.println("Month is " + calendar.get(GregorianCalendar.MONTH)); System.out.println("Date is " + calendar.get(GregorianCalendar.DATE));calendar.setTimeInMillis(1234567898765L);System.out.println("Year is " + calendar.get(GregorianCalendar.YEAR)); System.out.println("Month is " + calendar.get(GregorianCalendar.MONTH)); System.out.println("Date is " + calendar.get(GregorianCalendar.DATE)); }}9.6public class Exercise09_06 {static String output = "";/** Main method */public static void main(String[] args) {Scanner input = new Scanner(System.in);// Prompt the user to enter yearSystem.out.print("Enter full year (i.e. 2001): ");int year = input.nextInt();// Prompt the user to enter monthSystem.out.print("Enter month in number between 1 and 12: ");int month = input.nextInt();// Print calendar for the month of the yearprintMonth(year, month);System.out.println(output);}/** Print the calendar for a month in a year */static void printMonth(int year, int month) {// Get start day of the week for the first date in the monthint startDay = getStartDay(year, month);// Get number of days in the monthint numOfDaysInMonth = getNumOfDaysInMonth(year, month);// Print headingsprintMonthTitle(year, month);// Print bodyprintMonthBody(startDay, numOfDaysInMonth);}/** Get the start day of the first day in a month */static int getStartDay(int year, int month) {// Get total number of days since 1/1/1800int startDay1800 = 3;long totalNumOfDays = getTotalNumOfDays(year, month);// Return the start dayreturn (int)((totalNumOfDays + startDay1800) % 7);}/** Get the total number of days since Jan 1, 1800 */static long getTotalNumOfDays(int year, int month) {long total = 0;// Get the total days from 1800 to year -1for (int i = 1800; i < year; i++)if (isLeapYear(i))total = total + 366;elsetotal = total + 365;// Add days from Jan to the month prior to the calendar month for (int i = 1; i < month; i++)total = total + getNumOfDaysInMonth(year, i);return total;}/** Get the number of days in a month */static int getNumOfDaysInMonth(int year, int month) {if (month == 1 || month==3 || month == 5 || month == 7 ||month == 8 || month == 10 || month == 12)return 31;if (month == 4 || month == 6 || month == 9 || month == 11)return 30;if (month == 2)if (isLeapYear(year))return 29;elsereturn 28;return 0; // If month is incorrect.}/** Determine if it is a leap year */static boolean isLeapYear(int year) {if ((year % 400 == 0) || ((year % 4 == 0) && (year % 100 != 0))) return true;return false;}/** Print month body */static void printMonthBody(int startDay, int numOfDaysInMonth) { // Pad space before the first day of the monthint i = 0;for (i = 0; i < startDay; i++)output += " ";for (i = 1; i <= numOfDaysInMonth; i++) {if (i < 10)output += " " + i;elseoutput += " " + i;if ((i + startDay) % 7 == 0)output += "\n";}output += "\n";}/** Print the month title, i.e. May, 1999 */static void printMonthTitle(int year, int month) {output += " " + getMonthName(month)+ ", " + year + "\n";output += "-----------------------------\n";output += " Sun Mon Tue Wed Thu Fri Sat\n";}/** Get the English name for the month */static String getMonthName(int month) {String monthName = null;switch (month) {case 1: monthName = "January"; break;case 2: monthName = "February"; break;case 3: monthName = "March"; break;case 4: monthName = "April"; break;case 5: monthName = "May"; break;case 6: monthName = "June"; break;case 7: monthName = "July"; break;case 8: monthName = "August"; break;case 9: monthName = "September"; break;case 10: monthName = "October"; break;case 11: monthName = "November"; break;case 12: monthName = "December";}return monthName;}}9.7public class Exercise09_07 {public static void main (String[] args) {Account account = new Account(1122, 20000);Account.setAnnualInterestRate(4.5);account.withdraw(2500);account.deposit(3000);System.out.println("Balance is " + account.getBalance()); System.out.println("Monthly interest is " +account.getMonthlyInterest());System.out.println("This account was created at " +account.getDateCreated());}}class Account {private int id;private double balance;private static double annualInterestRate;private java.util.Date dateCreated;public Account() {dateCreated = new java.util.Date();}public Account(int newId, double newBalance) {id = newId;balance = newBalance;dateCreated = new java.util.Date();}public int getId() {return this.id;}public double getBalance() {return balance;}public static double getAnnualInterestRate() {return annualInterestRate;}public void setId(int newId) {id = newId;}public void setBalance(double newBalance) {balance = newBalance;}public static void setAnnualInterestRate(double newAnnualInterestRate) { annualInterestRate = newAnnualInterestRate;}public double getMonthlyInterest() {return balance * (annualInterestRate / 1200);}public java.util.Date getDateCreated() { return dateCreated;}public void withdraw(double amount) {balance -= amount;}public void deposit(double amount) {balance += amount;}}9.8public class Exercise09_08 {public static void main(String[] args) { Fan1 fan1 = new Fan1();fan1.setSpeed(Fan1.FAST);fan1.setRadius(10);fan1.setColor("yellow");fan1.setOn(true);System.out.println(fan1.toString());Fan1 fan2 = new Fan1();fan2.setSpeed(Fan1.MEDIUM);fan2.setRadius(5);fan2.setColor("blue");fan2.setOn(false);System.out.println(fan2.toString()); }}class Fan1 {public static int SLOW = 1;public static int MEDIUM = 2;public static int FAST = 3;private int speed = SLOW;private boolean on = false;private double radius = 5;private String color = "white";public Fan1() {}public int getSpeed() {return speed;}public void setSpeed(int newSpeed) {speed = newSpeed;}public boolean isOn() {return on;}public void setOn(boolean trueOrFalse) {this.on = trueOrFalse;}public double getRadius() {return radius;}public void setRadius(double newRadius) { radius = newRadius;}public String getColor() {return color;}public void setColor(String newColor) {color = newColor;}@Overridepublic String toString() {return"speed " + speed + "\n"+ "color " + color + "\n"+ "radius " + radius + "\n"+ ((on) ? "fan is on" : " fan is off"); }}public class Exercise09_09 {public static void main(String[] args) {RegularPolygon polygon1 = new RegularPolygon();RegularPolygon polygon2 = new RegularPolygon(6, 4);RegularPolygon polygon3 = new RegularPolygon(10, 4, 5.6, 7.8);System.out.println("Polygon 1 perimeter: " +polygon1.getPerimeter());System.out.println("Polygon 1 area: " + polygon1.getArea());System.out.println("Polygon 2 perimeter: " +polygon2.getPerimeter());System.out.println("Polygon 2 area: " + polygon2.getArea());System.out.println("Polygon 3 perimeter: " +polygon3.getPerimeter());System.out.println("Polygon 3 area: " + polygon3.getArea());}}class RegularPolygon {private int n = 3;private double side = 1;private double x;private double y;public RegularPolygon() {}public RegularPolygon(int number, double newSide) {n = number;side = newSide;}public RegularPolygon(int number, double newSide, double newX, double newY) {n = number;side = newSide;x = newX;y = newY;}public int getN() {return n;}public void setN(int number) {n = number;}public double getSide() {return side;}public void setSide(double newSide) {side = newSide;}public double getX() {return x;}public void setX(double newX) {x = newX;}public double getY() {return y;}public void setY(double newY) {y = newY;}public double getPerimeter() {return n * side;}public double getArea() {return n * side * side / (Math.tan(Math.PI / n) * 4); }}9.10public class Exercise09_10 {public static void main(String[] args) {Scanner input = new Scanner(System.in);System.out.print("Enter a, b, c: ");double a = input.nextDouble();double b = input.nextDouble();double c = input.nextDouble();QuadraticEquation equation = new QuadraticEquation(a, b, c);double discriminant = equation.getDiscriminant();if (discriminant < 0) {System.out.println("The equation has no roots");}else if (discriminant == 0){System.out.println("The root is " + equation.getRoot1());}else// (discriminant >= 0){System.out.println("The roots are " + equation.getRoot1()+ " and " + equation.getRoot2());}}}class QuadraticEquation {private double a;private double b;private double c;public QuadraticEquation(double newA, double newB, double newC) {a = newA;b = newB;c = newC;}double getA() {return a;}double getB() {return b;}double getC() {return c;}double getDiscriminant() {return b * b - 4 * a * c;}double getRoot1() {if (getDiscriminant() < 0)return 0;else {return (-b + getDiscriminant()) / (2 * a);}}double getRoot2() {if (getDiscriminant() < 0)return 0;else {return (-b - getDiscriminant()) / (2 * a);}}}9.11public class Exercise09_11 {public static void main(String[] args) {Scanner input = new Scanner(System.in);System.out.print("Enter a, b, c, d, e, f: ");double a = input.nextDouble();double b = input.nextDouble();double c = input.nextDouble();double d = input.nextDouble();double e = input.nextDouble();double f = input.nextDouble();LinearEquation equation = new LinearEquation(a, b, c, d, e, f);if (equation.isSolvable()) {System.out.println("x is " +equation.getX() + " and y is " + equation.getY());}else {System.out.println("The equation has no solution");}}}class LinearEquation {private double a;private double b;private double c;private double d;private double e;private double f;public LinearEquation(double newA, double newB, double newC, double newD, double newE, double newF) {a = newA;b = newB;c = newC;d = newD;e = newE;f = newF;}double getA() {return a;}double getB() {return b;}double getC() {return c;}double getD() {return d;}double getE() {return e;}double getF() {return f;}boolean isSolvable() {return a * d - b * c != 0;}double getX() {double x = (e * d - b * f) / (a * d - b * c);return x;}double getY() {double y = (a * f - e * c) / (a * d - b * c);return y;}}9.12public class Exercise09_12 {public static void main(String[] args) {Scanner input = new Scanner(System.in);System.out.print("Enter the endpoints of the first line segment: ");double x1 = input.nextDouble();double y1 = input.nextDouble();double x2 = input.nextDouble();double y2 = input.nextDouble();System.out.print("Enter the endpoints of the second line segment: ");double x3 = input.nextDouble();double y3 = input.nextDouble();double x4 = input.nextDouble();double y4 = input.nextDouble();// Build a 2 by 2 linear equationdouble a = (y1 - y2);double b = (-x1 + x2);double c = (y3 - y4);double d = (-x3 + x4);double e = -y1 * (x1 - x2) + (y1 - y2) * x1;double f = -y3 * (x3 - x4) + (y3 - y4) * x3;LinearEquation equation = new LinearEquation(a, b, c, d, e, f);if (equation.isSolvable()) {System.out.println("The intersecting point is: (" +equation.getX() + ", " + equation.getY() + ")");}else {System.out.println("The two lines do not cross ");}}}9.13public class Exercise09_13 {public static void main(String[] args) {Scanner input = new Scanner(System.in);System.out.print("Enter the number of rows and columns of the array: ");int numberOfRows = input.nextInt();int numberOfColumns = input.nextInt();double[][] a = new double[numberOfRows][numberOfColumns];System.out.println("Enter the array: ");for (int i = 0; i < a.length; i++)for (int j = 0; j < a[i].length; j++)a[i][j] = input.nextDouble();Location location = locateLargest(a);System.out.println("The location of the largest element is " + location.maxValue + " at ("+ location.row + ", " + location.column + ")");}public static Location locateLargest(double[][] a) {Location location = new Location();location.maxValue = a[0][0];for (int i = 0; i < a.length; i++)for (int j = 0; j < a[i].length; j++) {if (location.maxValue < a[i][j]) {location.maxValue = a[i][j];location.row = i;location.column = j;}}return location;}}class Location {int row, column;double maxValue;}9.14public class Exercise09_14 {public static void main(String[] args) {int size = 100000;double[] list = new double[size];for (int i = 0; i < list.length; i++) {list[i] = Math.random() * list.length;}StopWatch stopWatch = new StopWatch();selectionSort(list);stopWatch.stop();System.out.println("The sort time is " + stopWatch.getElapsedTime()); }/** The method for sorting the numbers */public static void selectionSort(double[] list) {for (int i = 0; i < list.length - 1; i++) {// Find the minimum in the list[i..list.length-1]double currentMin = list[i];int currentMinIndex = i;for (int j = i + 1; j < list.length; j++) {if (currentMin > list[j]) {currentMin = list[j];currentMinIndex = j;}}// Swap list[i] with list[currentMinIndex] if necessary;if (currentMinIndex != i) {list[currentMinIndex] = list[i];list[i] = currentMin;}}}}class StopWatch {private long startTime = System.currentTimeMillis(); private long endTime = startTime;public StopWatch() {}public void start() {startTime = System.currentTimeMillis();}public void stop() {endTime = System.currentTimeMillis();}public long getElapsedTime() {return endTime - startTime;}}。

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