大数据基础技能试题及答案

Java基础1. Which of the following will compile correctly?A) float f=10f;B) float f=10.1;C) float f=10.1f;D) byte b=10b;2. Which declarations of identifiers are legalA. $personsB. TwoUsersC. *pointD. thisE. _endline3. Which statement of assigning a long type variable to a hexadecimal value is correctA. long number = 345L;B. long number = 0345;C. long number = 0345L;D. long number = 0x345L4. Which of the following fragments might cause errorsA. String s = "Gone with the wind";String t = " good ";String k = s + t;B. String s = "Gone with the wind";String t;t = s[3] + "one";C. String s = "Gone with the wind";String standard = s.toUpperCase();D. String s = "home directory";String t = s - "directory";5. Which are syntactically valid statement at// point xclass Person {private int a;public int change(int m){ return m; }}public class Teacher extends Person {public int b;public static void main(String arg[]){Person p = new Person();Teacher t = new Teacher();int i;// point x}}A. i = m;B. i = b;C. i = p.a;D. i = p.change(30);E. i = t.b.6. Which layout manager is used when the frame is resized the buttons's position in the Frame might be changedA. BorderLayoutB. FlowLayoutC. CardLayoutD. GridLayout7. Given the following code fragment:1) public void create() {2} Vector myVect;3} myVect = new Vector();4} }Which of the following statements are trueA. The declaration on line 2 does not allocate memory space for the variable myVect.B. The declaration on line 2 allocates memory space for a reference to a Vector object.C. The statement on line 2 creates an object of class Vector.D. The statement on line 3 creates an object of class Vector.E. The statement on line 3 allocates memory space for an object of class Vector8. Which of the following answer is correct to express the value 8 in octal numberA. 010B. 0x10C. 08D. 0x89. Which are not Java keywordsA. TRUEB. sizeofC. constD. superE. void10. Which of the following statements are trueA. The equals() method determines if reference values refer to the same object.B. The == operator determines if the contents and type of two separate objects match.C. The equals() method returns true only when the contents of two objects match.D. The class File overrides equals() to return true if the contents and type of two separate objects match.11. Which statements about inheritance are trueA. In Java programming language only allows single inheritance.B. In Java programming language allows a class to implement only oneinterface.C. In Java programming language a class cannot extend a class and implementa interface together.D. In Java programming language single inheritance makes code morereliable.12.1) class Person {2} public void printValue(int i, int j) {/*…*/ }3} public void printValue(int i){/*...*/ }4} }5) public class Teacher extends Person {6} public void printValue() {/*...*/ }7} public void printValue(int i) {/*...*/}8} public static void main(String args[]){9} Person t = new Teacher();10} t.printValue(10);11} }12} }Which method will the statement on line 10 callA. on line 2B. on line 3C. on line 6D. on line 713. Which are not Java primitive typesA. shortB. BooleanC. unitD. float14、The method resume() is responsible for resuming which thread's executionA. The thread which is stopped by calling method stop()B. The thread which is stopped by calling method sleep()C. The thread which is stopped by calling method wait()\D. The thread which is stopped by calling method suspend()15. Which of the following range of int is correctA. -2^7 – 2^7-1B. 0 – 2^32-1C. -2^15 – 2^15-1D. -2^31 – 2^31-116. Which keyword should be used to enable interaction with the lock of anobject The flag allows exclusive access to that object.A. transientB. synchronizedC. serializeD. static17. Which is the return type of the method main()A. intB. voidC. booleanD. static18. Given the following code:if (x>0) { System.out.println("first"); }else if (x>-3) { System.out.println("second"); }else { System.out.println("third"); }Which range of x value would print the string "second"A. x > 0B. x > -3C. x <= -3D. x <= 0 & x > -319、Which of the following answer is correct to express the value 10 in hexadecimal numberA. 0xAB. 0x16C. 0AD. 01620. Which statements about the garbage collection are trueA. The program developer must create a thread to be responsible for freethe memory.B. The garbage collection will check for and free memory no longer needed.C. The garbage collection allow the program developer to explicity andimmediately free the memory.D. The garbage collection can free the memory used java object at expecttime.21、Given the following code:1) public class Test {2} int m, n;3} public Test() {}4} public Test(int a) { m=a; }5} public static void main(String arg[]) {6} Test t1,t2;7} int j,k;8} j=0; k=0;9} t1=new Test();10} t2=new Test(j,k);11} }12} }Which line would cause one error during compilationA. line 3B. line 5C. line 6D. line 1022、Given the uncompleted code of a class:class Person {String name, department;int age;public Person(String n){ name = n; }public Person(String n, int a){ name = n; age = a; }public Person(String n, String d, int a) {// doing the same as two arguments version of constructor// including assignment name=n,age=adepartment = d;}}Which expression can be added at the "doing the same as..." part of the constructorA. Person(n,a);B. this(Person(n,a));C. this(n,a);D. this(name,age).23、Which of the following statements about variables and their scopes are trueA. Instance variables are member variables of a class.B. Instance variables are declared with the static keyword.C. Local variables defined inside a method are created when the method is executed.D. Local variables must be initialized before they are used.24、public void test() {try { oneMethod();System.out.println("condition 1");} catch (ArrayIndexOutOfBoundsException e) {System.out.println("condition 2");} catch(Exception e) {System.out.println("condition 3");} finally {System.out.println("finally");}}Which will display if oneMethod run normallyA. condition 1B. condition 2C. condition 3D. finally25、Given the following code:public class Test {void printValue(int m){do { System.out.println("The value is"+m);}while( --m > 10 )}public static void main(String arg[]) {int i=10;Test t= new Test();t.printValue(i);}}Which will be outputA. The value is 8B. The value is 9C. The value is 10D. The value is 1126、Which of the following statements about declaration are trueA. Declaration of primitive types such as boolean, byte and so on does not allocate memory space for the variable.B. Declaration of primitive types such as boolean, byte and so on allocates memory space for the variable.C. Declaration of nonprimitive types such as String, Vector and so on does not allocate memory space for the object.D. Declaration of nonprimitive types such as String, Vector ans so on allocates memory space for the object.27、In the Java API documentation which sections are included in a class documentA. The description of the class and its purposeB. A list of methods in its super classC. A list of member variableD. The class hierarchy28、Given the following code:1) public void modify() {2) int i, j, k;3) i = 100;4) while ( i > 0 ) {5) j = i * 2;6) System.out.println (" The value of j is " + j );7) k = k + 1;8) i--;9) }10} }Which line might cause an error during compilationA. line 4B. line 6C. line 7D. line 829、Which of the following statements about variables and scope are trueA. Local variables defined inside a method are destroyed when the method is exited.B. Local variables are also called automatic variables.C. Variables defined outside a method are created when the object is constructed.D. A method parameter variable continues to exist for as long as the object is needed in which the method is defined.30、A class design requires that a member variable cannot be accessible directly outside the class. Which modifier should be used to obtain the access controlA. publicB. no modifierC. protectedD. private31、Given the following code fragment:1) String str = null;2) if ((str != null) && (str.length() > 10)) {3} System.out.println("more than 10");4} }5) else if ((str != null) & (str.length() < 5)) {6} System.out.println("less than 5");7} }8) else { System.out.println("end"); }Which line will cause errorA. line 1B. line 2C. line 5D. line 832、Which statements about Java code security are trueA. The bytecode verifier loads all classes needed for the execution of a program.B. Executing code is performed by the runtime interpreter.C. At runtime the bytecodes are loaded, checked and run in an interpreter.D. The class loader adds security by separating the namespaces for the classes of the local file system from those imported from network sources.33、Given the following code:public class Person{int arr[] = new int[10];public static void main(String a[]) {System.out.println(arr[1]);}}Which statement is correctA. When compilation some error will occur.B. It is correct when compilation but will cause error when running.C. The output is zero.D. The output is null.34、public class Parent {public int addValue( int a, int b) {int s;s = a+b;return s;}}class Child extends Parent {}Which methods can be added into class ChildA. int addValue( int a, int b ){// do something...}B. public void addValue (){// do something...}C. public int addValue( int a ){// do something...}D. public int addValue( int a, int b )throws MyException {//do something...}35、Which statements about thread are trueA. Once a thread is created, it can star running immediately.B. To use the start() method makes a thread runnable, but it does not necessarily start immediately.C. When a thread stops running because of pre-emptive, it is placed at the front end of the runnable queue.D. A thread may cease to be ready for a variety of reasons.36、A member variable defined in a class can be accessed only by the classes in the same package. Which modifier should be used to obtain the access controlA. privateB. no modifierC. publicD. protected37、A public member vairable called MAX_LENGTH which is int type, the value of the variable remains constant value 100. Use a short statement to define the variable.A. public int MAX_LENGTH=100;B. final int MAX_LENGTH=100;C. final public int MAX_LENGTH=100;D. public final int MAX_LENGTH=100.38、Which expressions are correct to declare an array of 10 String objectsA. char str[];B. char str[][];C. String str[];D. String str[10];39、Which fragments are correct in Java source fileA. package testpackage;精选文库public class Test{//do something...}B. import java.io.*;package testpackage;public class Test{// do something...}C. import java.io.*;class Person{// do something...}public class Test{// do something...}D. import java.io.*;import java.awt.*;public class Test{// do something...}40：String s= "hello";String t = "hello";char c[] = {'h','e','l','l','o'} ;Which return trueA. s.equals(t);B. t.equals(c);C. s==t;D. t.equals(new String("hello"));E. t==c.41. Which of the following statements are legalA. long l = 4990;B. int i = 4L;C. float f = 1.1;D. double d = 34.4;E. double t = 0.9F.42、public class Parent {int change() {…}}class Child extends Parent {}Which methods can be added into class ChildA. public int change(){}B. int chang(int i){}C. private int change(){}D. abstract int chang(){}精选文库43、class Parent {String one, two;public Parent(String a, String b){one = a;two = b;}public void print(){ System.out.println(one); }}public class Child extends Parent {public Child(String a, String b){super(a,b);}public void print(){System.out.println(one + " to " + two);}public static void main(String arg[]){Parent p = new Parent("south", "north");Parent t = new Child("east", "west");p.print();t.print();}}Which of the following is correctA. Cause error during compilation.B. southeastC. south to northeast to westD. south to northeastE. southeast to west44、Given the uncompleted method:1)2) { success = connect()3} if (success==-1) {4} throw new TimedOutException();5} }6}}TimedOutException is not a RuntimeException. Which can complete the method of declaration when added at line 1精选文库A. public void method()B. public void method() throws ExceptionC. public void method() throws TimedOutExceptionD. public void method() throw TimedOutExceptionE. public throw TimedOutException void method()45、Given the following code:1) class Parent {2} private String name;3} public Parent(){}4} }5) public class Child extends Parent {6} private String department;7} public Child() {}8} public String getValue(){ return name; }9) public static void main(String arg[]) {10} Parent p = new Parent();11} }12) }Which line will cause errorA. line 3B. line 6C. line 7D. line 8E. line 1046、The variable "result" is boolean. Which expressions are legalA. result = true;B. if ( result ) { // do something... }C. if ( result!= 0 ) { // so something... }D. result = 147、Class Teacher and Student are subclass of class Person.Person p;Teacher t;Student s;p, t and s are all non-null.if(t instanceof Person) { s = (Student)t; }What is the result of this sentenceA. It will construct a Student object.B. The expression is legal.C. It is illegal at compilation.D. It is legal at compilation but possible illegal at runtime.48、Given the following class:public class Sample{long length;public Sample(long l){ length = l; }public static void main(String arg[]){Sample s1, s2, s3;s1 = new Sample(21L);s2 = new Sample(21L);s3 = s2;long m = 21L;}}Which expression returns trueA. s1 == s2;B. s2 == s3;C. m == s1;D. s1.equals(m).49、Which classes can be used as the argument of the constructor of the class FilterInputStreamA. FilterOutputStreamB. FileC. InputStreamD. RandomAccessFile50、Which classes can be used as the argument of the constructor of the class FileInputStreamA. InputStreamB. FileC. FileOutputStreamD. String51、Which is not a method of the class InputStreamA. int read(byte[])B. void flush()C. void close()D. int available()52、Given the following code:class Person {String name,department;public void printValue(){System.out.println("name is "+name);System.out.println("department is "+department);}}public class Teacher extends Person {int salary;public void printValue(){// doing the same as in the parent method printValue()// including print the value of name and department.System.out.println("salary is "+salary);}}Which expression can be added at the "doing the same as..." part of the method printValue()A. printValue();B. this.printValue();C. person.printValue();D. super.printValue().53. Which of the following assignment is not correctA. float f = 11.1;B. double d = 5.3E12;C. double d = 3.14159;D. double d = 3.14D.Linux基础1. Linux文件权限一共10位长度，分成四段，第三段表示的内容是__。