JAVA题库:格林模拟试题一（下）(8)

question 55)

you are concerned that your program may attempt to use more memory than is available. to avoid this situation you want to ensure that the java virtual machine will run its garbage collection just before you start a complex routine. what can you do to be certain that garbage collection will run when you want .

1) you cannot be certain when garbage collection will run
2) use the runtime.gc() method to force garbage collection
3) ensure that all the variables you require to be garbage collected are set to null
4) use the system.gc() method to force garbage collectionx2s

question 56)

you are using the gridbaglayout manager to place a series of buttons on a frame. you want to make the size of one of the buttons bigger than the text it contains. which of the following will allow you to do that?

1) the gridbaglayout manager does not allow you to do this
2) the setfill method of the gridbaglayout class
3) the setfill method of the gridbagconstraints class
4) the fill field of the gridbagconstraints class 

question 57)

which of the following most closely describes a bitset collection?

1) a class that contains groups of unique sequences of bits
2) a method for flipping individual bits in instance of a primitive type
3) an array of boolean primitives that indicate zeros or ones
4) a collection for storing bits as on-off information, like a vector of bits

question 58)
you have these files in the same directory. what will happen when you attempt to compile and run class1.java if you have not already compiled base.java

//base.java
package base;
class base{
    protected void amethod(){
 system.out.println("amethod");
    }//end of amethod
}//end of class base
package class1;
//class1.java
public class class1 extends base{
    public static void main(string argv[]){
 base b = new base();
 b.amethod();
    }//end of main

}//end of class1

1) compile error: methods in base not found
2) compile error: unable to access protected method in base class
3) compilation followed by the output "amethod"
4)compile error: superclass class1.base of class class1.class1 not found

question 59)

what will happen when you attempt to compile and run the following code

class base{
    private void amethod(int ibase){
 system.out.println("base.amethod");
    }
}



class over extends base{
    public static void main(string argv[]){
 over o = new over();
 int ibase=0;
 o.amethod(ibase);
    }

    public void amethod(int iover){
 system.out.println("over.amethod");
    }
}

1) compile time error complaining that base.amethod is private
2) runtime error complaining that base.amethod is private
3) output of "base.amethod"
4) output of "over.amethod" 

question 60)

you are creating an applet with a frame that contains buttons. you are using the gridbaglayout manager and you have added four buttons. at the moment the buttons appear in the centre of the frame from left to right. you want them to appear one on top of the other going down the screen. what is the most appropriate way to do this.
 

1) set the gridy value of the gridbagconstraints class to a value increasing from 1 to 4
2) set the fill value of the gridbagconstraints class to vertical
3) set the ipady value of the gridbagconstraints class to a value increasing from 0 to 4
4) set the fill value of the gridbaglayouts class to gridbag.vertical