JAVA练习题含答案-answers to practice 2

Multiple Choice1)Which operator is used to concatenate two strings?(a)+(b)–(c)*(d)/Answer: A (see page 35)2)Which operator returns the remainder of integer division?(a)%(b)/(c)*(d)none of the aboveAnswer: A (see page 26)3)What is the value of the variable c in the statements that follow?String phrase = "Make hay while the sun is shining.";char c = phrase.charAt(10);(a)w(b)h(c)i(d)None of the aboveAnswer: B (see page 40)4)The escape sequence the represents the new-line character is:(a)\r(b)\t(c)\n(d)\\Answer: C (see page 43)5)The syntax that declares a Java named constant named SALES_TAX is:(a)double SALES_TAX = 7.50;(b)public double SALES_TAX = 7.50;(c)public static double SALES_TAX = 7.50;(d)public static final double SALES_TAX = 7.50;Answer: D (see page 47)6)In Java, a block comment is delimited by:(a)*/ /*(b)/* /*(c)/* */(d)*/ */Answer: C (see page 50)7)To mark a block comment for inclusion in the Javadoc documentation, the block must bedelimited by:(a)/** */(b)*/* */(c)**/ /*(d)**/ */Answer: A (see page 50)8)Valid arguments to the System.out object‟s println method include:(a) “Anything with double quotes”(b) String variables(c) Variables of type int(d) All of the aboveAnswer: D (see page 59)9)Which statement or group of statements produces the output: Java programming is fun!(a)System.out.print(Java programming);System.out.print(is fun!);(b)System.out.println(Java programming is fun!);(c)System.out.println(“Java programming”);System.out.println(“ is fun!”);(d)System.out.print(“Java programming”)System.out.println(“ is fun!”);Answer: D (see page 60)10)If a hyphen is added after the % in a format specifier, the output will be _________.(a)Left justified(b)Right justified(c)Centered(d)None of the aboveAnswer: A (see page 64)11)The statement: System.out.printf("%6.2f", 597.7231); displays:(a)597.723(b)597.72(c)000597.72(d)None of the aboveAnswer: B (see page 64)12)The Java method printf is based on the ________ language.(a)Pascal(b)C++(c)C(d)ADAAnswer: C (see page 67)13)The class NumberFormat allows you to specify a constant representing which country‟scurrency format should be used. To use this constant you must import:(a)java.util.Locale(b)java.util.Currency(c)java.util.Properties(d)None of the above.Answer: A (see page 71)14)Standard code libraries in Java are called:(a)Methods(b)Classes(c)Packages(d)StatementsAnswer: C (see page 72)15)What Java package includes the class Scanner?(a)awt(b)swing(c)io(d)utilAnswer: D (see page 78)True/False1)Objects of type String are strings of characters that are written within single quotes.Answer:False (see page 34)2)In Java, Strings are immutable objects. Immutable objects can be changed.Answer:False (see page 44)3)An advantage of using the Unicode character set is that it easily handles languages otherthan English.Answer:True (see page 44)4)Java uses the ASCII character set.Answer:False (see page 44)1)Efficiency is lost in importing the entire package instead of importing the classes youuse.Answer:False (see page 73)2)Every Java program automatically imports the java.util package.Answer:False (see page 73)3)The new line character is represented as …\n‟.Answer:True (see page 61)4)The method printf is used the same way as the method println but has the added featurethat allows you to add formatting instructions.Answer:False (see page 61)5)The printf method can be used to output multiple formatted values.Answer:True (see page 64)6)The Scanner class has a method next that allows an entire line of string text to be read.Answer:False (see page 80)7)Echoing input is good programming practice because it can reveal problems in the input.Answer:True (see page 80)Short Answer/Essay1)How is the % (modulus) operator used? What is the common use of the modulusoperator?Answer:The modulus operator is used to return the remainder in integer division. For example, the modulus operator is commonly used to determine if a number is an even or an odd value.2)What is the output of the following Java statements?//String method examplesString str = "Java Programming!";System.out.println(str.equals("Java Programming!"));System.out.println(str.toLowerCase());System.out.println(str.toUpperCase());System.out.println(str.substring(5,8));System.out.println(stIndexOf("m"));Answer:truejava programming!JAVA PROGRAMMING!Pro123)Write a Java statement to access the 7th character in the String variable myString andplace it in the char variable c.Answer:c = myString.charAt(6);4)Write a Java statement to determine the length of a string variable called input. Store theresult in an integer variable called strLength.Answer:int strLength = input.length();5)Write ONE Java statement to display your first and last name on two separate lines.Answer:System.out.print("Wally\nWonders");6)Write a complete Java console application that prompts the user for two numbers,multiplies the numbers, and then displays the result to the user.Answer:import java.util.Scanner;public class ConsoleMultiply{public static void main(String[] args){//Create the scanner object for console inputScanner keyboard = new Scanner(System.in);//Prompt the user for the first numberSystem.out.print("Enter the first integer: ");//Read the inputint firstNumber = keyboard.nextInt();//Prompt the user for the second numberSystem.out.print("Enter the second integer: ");//Read the second numberint secondNumber = keyboard.nextInt();System.out.println(firstNumber + "*" + secondNumber + " is "+ firstNumber * secondNumber);}}7)Write a Java statement to create and initialize a Scanner object named input.Answer:Scanner input = new Scanner(System.in);8)Consider the following code snippet.int i = 10;int n = i++%5;1）What are the values of i and n after the code is executed?Answer:i is 11, and n is 0.2）What are the final values of i and n if instead of using the postfix increment operator (i++), you use the prefix version (++i))?Answer: i is 11, and n is 1.9)Programming projects : question 2 and 3 (see page 93)import java.util.Scanner;public class Question2{public static void main(String[] args){// Variable declarationsScanner scan = new Scanner(System.in);String first;String last;System.out.println("Enter your first name:");first = scan.nextLine();System.out.println("Enter your last name:");last = scan.nextLine();System.out.println(first + " " + last + " turned to Pig Latin is:");// First convert first name to pig latinString pigFirstName = first.substring(1,first.length()) + first.substring(0,1) + "ay";// Then capitalize first letterpigFirstName = pigFirstName.substring(0,1).toUpperCase() +pigFirstName.substring(1,pigFirstName.length());// Repeat for the last nameString pigLastName = last.substring(1,last.length()) + last.substring(0,1) + "ay";// Then capitalize first letterpigLastName = pigLastName.substring(0,1).toUpperCase() +pigLastName.substring(1,pigLastName.length());System.out.println(pigFirstName + " " + pigLastName);}} // Question2import java.util.Scanner;public class Question3{public static void main(String[] args){Scanner keyboard = new Scanner(System.in);System.out.println("Enter first number to add:");int first = keyboard.nextInt();System.out.println("Enter second number to add");int second = keyboard.nextInt();int result = first + second;System.out.println("Adding " + first + " + " + second + " equals " + result);System.out.println("Subtracting " + first + " - " + second + " equals " + (first - second));System.out.println("Multiplying " + first + " * " + second + " equals " + (first * second));}} // Question3。