Sunday, February 5, 2012

SCJP model question answer page 1


1)
Class C {
            public static void main(String[] args)
                        {
                        int[]a1[]=new int[3][3]; //3
                        int a2[4]={3,4,5,6}; //4
                        int a2[5]; //5

                        }
            }

What is the result of attempting to compile and run the program ?.

1.compiletime error at lines 3,4,5

2.compiltime error at line 4,5

3.compiletime error at line 3

4.Runtime Exception

5.None of the above

Ans: 2
Explanation:
no value shoud be specified in the rightsidebrackets when constructing an array


2)
interface I
{
            void f1(); // 1
            public void f2(); // 2
            protected void f3(); // 3
            private void f4(); // 4
}

which lines generate compile time errors?

1.compiletime error at lines 1,2,3,4

2.compiletime error at line 3

3.compiletime error at line 1

4.compiletime error at lines 3,4

5.None of the above

Answer: 4
Explanation:
all methods declared within an interface are implicitly public, a weaker access level can not be declared.

3)
class C{
            int i;
            public static void main (String[] args) {
            int i; //1
            private int a = 1; //2
            protected int b = 1; //3
            public int c = 1; //4
            System.out.println(a+b+c); //5

}}

1.compiletime error at lines 1,2,3,4,5

2 compiletime error at lines 2,3,4,5

3.compiletime error at lines 2,3,4

4.prints 3

5.None of the above

Answer  2
Explanation:
The access modifiers public, protected and private, can not be applied to variables declared inside methods.

4)
Class C {
            public static void main (String[] a1) {
            System.out.print(a1[1] + a1[2] + a1[3]);
}}

What is the result of attempting to compile and run the program?

java command A B C

1.Prints: ABC

2.Prints BC and Runtime Exception

3.Prints: BCD

4.Runtime Exception

5.None of the above

Answer 2
Explanation:
array index outof bounds exception only till a1[2] is allowed.
5)

class C{
            static int s;
            public static void main(String a[]){
            C obj=new C();
            obj.m1();
            System.out.println(s);
            }
void m1();
{
            int x=1;
            m2(x);
            System.out.println(x+"");
}

void m2(int x)
{
            x=x*2;
            s=x;
}
}

1.prints 1,2

2.prints 2,0

3.prints 2,2

4.compile time error

5.Noneofthe above

Answer: 1
Explanation:
Only objects and arrays are passed by reference.other are passed by value.s is a static variable which is global to the class

6)
class C {
            public static void main(String[] args)
            {
            int i1=1;
            switch(i1)
            {
            case 1:
            System.out.println("one");
            case 2:
            System.out.println("two");
            case 3:
            System.out.println("three");
}}}

What is the result of attempting to compile and run the program?

1.prints one two three

2.prints one

3.compile time error

4.Runtime exceptionf

5.None of the above

Answer: 1
Explanation:
There is no break statement in case 1 so it causes the below case statements to execute regardless of their values

7)
 Each element must be unique
 Duplicate elements must not replace old elements.
 Elements are not key/value pairs.
 Accessing an element can be almost as fast as performing a similar operation on an array.
 Which of these classes provide the specified features?

1.LinkedList

2.TreeMap

3.HashMap

4.HashSet

5.None of the above
Answer: 4

8)
class C1
{
            static interface I
            {
            static class C2
            {
            }

}

public static void main(String a[])
{
C1.I.C2 ob1=new C1.I.C2();
System.out.println("object created");
}
}

What is the result of attempting to compile and run the program?

1.prints object created

2.Compile time error

3.Runtime Excepion

4.None of the above

Answer: 1
Explanation:
A static interface or class can contain static members.Static members can be accessed without instantiating the particular class

9)
class C1
{
static class C2
{
            static int i1;
}
public static void main(String a[])
{
            System.out.println(C1.C2.i1);
}
}

What is the result of attempting to compile and run the program?

1.prints 0

2.Compile time error

3.Runtime exception

4.None of the above

Answer: 1
Explanation:
static members can be accessed without instantiating the particular class

10)
A signed data type has an equal number of non-zero positive and negative values available

1.true

2.false

Answer: 2
Explanation:
The range of negative numbers is greater by 1 than the range of positive numbers

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