JAVA认证

question 45

what will happen when you try compiling and running this code?

public class ref{

public static void main(string argv[]){

ref r = new ref();

r.amethod(r);

}

public void amethod(ref r){

int i=99;

multi(r);

system.out.println(i);

}

public void multi(ref r){

r.i = r.i*2;

}

}

1) error at compile time

2) an output of 99

3) an output of 198

4) an error at runtime

answer to question 45

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question 46)

you need to create a class that will store unique object elements. you do not need to sort these elements but they must be unique.

what interface might be most suitable to meet this need?

1)set

2)list

3)map

4)vector

answer to question 46

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question 47)

which of the following will successfully create an instance of the vector class and add an element?

1) vector v=new vector(99);

v[1]=99;

2) vector v=new vector();

v.addelement(99);

3) vector v=new vector();

v.add(99);

4 vector v=new vector(100);

v.addelement('99');

answer to question 47

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question 48)

you have created a simple frame and overridden the paint method as follows

public void paint(graphics g){

g.drawstring('dolly',50,10);

}

what will be the result when you attempt to compile and run the program?

1) the string 'dolly' will be displayed at the centre of the frame

2) an error at compilation complaining at the signature of the paint method

3) the lower part of the word dolly will be seen at the top of the frame, with the top hidden.

4) the string 'dolly' will be shown at the bottom of the frame.

answer to question 48

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question 49)

what will be the result when you attempt to compile this program?

public class rand{

public static void main(string argv[]){

int irand;

irand = math.random();

system.out.println(irand);

}

}

1) compile time error referring to a cast problem

2) a random number between 1 and 10

3) a random number between 0 and 1

4) a compile time error about random being an unrecognised method

answer to question 49

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