1.Which statement about the garbage collection mechanism are true? A.Garbage collection require additional PRogram code in cases where multiple threads are running. B.The programmer can indicate that a reference through a local variable is no longer of interest. C.The programmer has a mechanism that eXPlicit and immediately frees the memory used by Java objects. D.The garbage collection mechanism can free the memory used by Java Object at expectable time. E.The garbage collection system never reclaims memory from objects while are still accessible to running user threads.
2. Give the following method: 1)public void method( ){ 2) String a,b; 3) a=new String(“hello world”); 4) b=new String(“game over”); 5) System.out.println(a+b+”ok”); 6) a=null; 7) a=b; System.out.println(a); 9) } In the absence of compiler optimization, which is the earliest point the object a referred is definitely hand to be garbage collection. A. before line 3 B.before line 5 C. before line 6 D.before line 7 E. Before line 9
3. Which statement about listener is true? A.Most component allow multiple listeners to be added. B.If multiple listener be add to a single component, the event only affected one listener. C.Component don’t allow multiple listeners to be add. D.The listener mechanism allows you to call an addXXXListener method as many times as is needed, specifying as many different listeners as your design require.
4.Give the following code: public class Example{ public static void main(String args[] ){ int l=0; do{ System.out.println(“Doing it for l is:”+l); }while(--l>0) System.out.println(“Finish”); } } Which well be output: A. Doing it for l is 3B. Doing it for l is 1C. Doing it for l is 2 D. Doing it for l is 0E. Doing it for l is –1F. Finish
5. Give the code fragment: 1)switch(x){ 2) case 1: System.out.println(“Test 1”);break; 3) case 2: 4) case 3: System.out.println(“Test 2”);break; 5) default: System.out.println(“end”); 6) } which value of x would cause “Test 2” to the output: A. 1B. 2C. 3D. default
6. Give incompleted method: 1) 2){if(unsafe()){//do something…} 3)else if(safe()){//do the other…} 4)} The method unsafe() will throw an IOException, which completes the method of declaration when added at line one? A.public IOException methodName() B.public void methodName() C.public void methodName() throw IOException D.public void methodName() throws IOException E.public void methodName() throws Exception
7. Give the code fragment: if(x>4){ System.out.println(“Test 1”);} else if (x>9){ System.out.println(“Test 2”);} else { System.out.println(“Test 3”);} Which range of value x would prodUCe of output “Test 2”? A. x<4B. x>4C. x>9D. None
8. Give the following method: public void example(){ try{ unsafe(); System.out.println(“Test1”); }catch(SafeException e){System.out.println(“Test 2”); }finally{System.out.println(“Test 3”);} System.out.println(“Test 4”); Which will display if method unsafe () run normally? A. Test 1B. Test 2C. Test 3D. Test 4 9. Which method you define as the starting point of new thread in a class from which new the thread can be execution? A. public void start()B. public void run()C. public void int() D. public static void main(String args[])E. public void runnable()
10.Given the following class definition: class A{ protected int i; A(int i){ this.i=i; } } which of the following would be a valid inner class for this class? Select all valid answers: A. class B{ } B.class B extends A{ } C.class B extends A{ B(){System.out.println(“i=”+i);} } D.class B{ class A{} } E.class A{}
11. Which modifier should be applied to a method for the lock of object this to be oBTained prior to execution any of the method body? A. synchronizedB. abstractC. finalD. staticE. public
12. The following code is entire contents of a file called Example.java,causes precisely one error during compilation: 1)class SubClass extends BaseClass{ 2) } 3)class BaseClass(){ 4) String str; 5) public BaseClass(){ 6) System.out.println(“ok”);} 7) public BaseClass(String s){ str=s;} 9)} 10)public class Example{ 11) public void method(){ 12) SubClass s=new SubClass(“hello”); 13) BaseClass b=new BaseClass(“world”); 14) } 15) }
Which line would be cause the error? A. 9B. 10C. 11D.12 13. Which statement is correctly declare a variable a which is suitable for refering to an array of 50 string empty object? A. String [] aB. String a[]C. char a[][]D. String a[50]F. Object a[50]
14. Give the following java source fragment: //point x public class Interesting{ //do something } Which statement is correctly Java syntax at point x? A. import java.awt.*;B.package mypackage;C. static int PI=3.14 D. public class MyClass{//do other thing…}E. class MyClass{//do something…}
15. Give this class outline: class Example{ private int x; //rest of class body… } Assuming that x invoked by the code java Example, which statement can made x be directly accessible in main() method of Example.java? A. change private int x to public int xB. change private int x to static int x C. change private int x to protected int xD. change private int x to final int x
16. A class design requires that a member variable should be accessible only by same package, which modifier Word should be used? A. protectedB. publicC. no modifierD. private
17. Which modifier should be applied to a declaration of a class member variable for the value of variable to remain constant after the creation of the object?
18. Which is corrected argument of main() method of application? A. String argsB. String ar[]C. Char args[][]D. StringBuffer arg[]
19. “The Employee object is a Person, An Employee has appointment store in a vector, a hire date and a number of dependent” short answer: use shortest statement declare a class of Employee.
20. Give the following class definition inseparate source files: public class Example{ public Example(){//do something} protected Example(int i){//do something} protected void method(){//do something} } public class Hello extends Example{//member method and member vari
