1. Which of the following are valid assignment expressions, given the following declarations:-

byte b;
int i = 10;
long l = 20;
1. b = i;
2. b += i;
3. b++;
4. b = b + i;
Answer


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2. State true or false: Interface methods can be declared static
1. true
2. false
Answer


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3. Select the correct answers: If you define a class within an interface,
1. the class is always public
2. the class is always static
3. the class methods cannot call methods declared in the interface
Answer


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4. State true or false: An abstract class can have a constructor
1. true
2. false
Answer


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5. What is the output of the following piece of code:



class	A {
	public	A() {
		class	B{
			B()	{
				System.out.println("In no-arg constructor");
			}
		}
		new B();
	}
	public	A(int a) {
		class	B{
			B()	{
				System.out.println("In constructor with an int argument");
			}
		}
		new B();
	}
	public	static void	main(	String[] args{
		A a1 = new	A();
		A a2 = new	A(10);
	}
}

1. Code does not compile
2. Code compiles but generates exception at runtime
3. Code compiles successfully and outputs



In no-arg constructor

In constructor with an int argument

Answer


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6. Select all correct answers: Numeric operators that throw the ArithmeticException on integer operands include
1. +
2. -
3. /
4. %
5. *
Answer


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7. What is the output of the following piece of code.



System.out.println("-0.0 == 0.0 returns " + (-0.0 == 0.0));

System.out.println("0.0 > -0.0 returns " + (0.0 > -0.0));

___________________________________

Answer


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8. Select true or false: The equality operator (==) always returns false if either operand is Nan and the inequality operator (!=) return true if either operand is Nan.
1. true
2. false
Answer


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9. Select the correct answers: You can use an instance of a File class to do the following
1. delete a file
2. change current working directory
3. rename files
4. create new sub-directories
Answer


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10. What is the output of the following code:



public	class	Temp{
	public	static void main(String[] args){
		String[] a = null;
		System.out.println("The length of the array is " + a.length):
	}
}

1. The code does not compile
2. The code compiles and prints out "The length of the array is 0";
3. The code compiles and prints out "The length of the array is null";
4. The code compiles but generates the NullPointerException at runtime
Answer


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11. Given the following declaration:

char a;

Which of the following are valid values that can be assigned to a?

1. ‘\0’
2. ‘\u003c’
3. ‘\349’
4. \u004
5. ‘\345’
Answer


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12. Given the following code, what is the output generated



class	Base {
	public	static void amethod(){
		System.out.println("In base amethod");
	}
	public	void another(){
		System.out.println("In base another");
	}
	static	int staticInt = 10;
	int	instanceVar = 20;
}
public	class	Child extends Base {
	public	static void amethod(){
		System.out.println("In child amethod");
	}
	public	void another() {
		System.out.println("In child another");
	}
	static	int staticInt = 30;
	int	instanceVar = 40;
	public	static void main(String[] a ){
		Base b = new Child();
		b.amethod();
		b.another();
		System.out.println("Value of staticInt is = " + b.staticInt);
		System.out.println("Value of instanceVar is = " + b.instanceVar);
	}
}

1. Code does not compile
2. Code compiles and prints out

 

 
 
 
 
 

In base amethod

In child another

Value of staticInt is 30

Value of instanceVar is 40

3. Code compiles and prints out

 

 
 
 
 
 

In base amethod

In child another

Value of staticInt is 10

Value of instanceVar is 20

4. Code compiles and prints out

 

 
 
 
 
 

In child amethod

In child another

Value of staticInt is 30

Value of instanceVar is 40

Answer


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13. Select all correct answers: Modifiers that you CANNOT use with constructors include
1. private
2. abstract
3. static
4. public
5. final
Answer


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14. State true or false: The RandomAccessFile class is compatible with the Stream classes
1. True
2. False
Answer


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15. What is the output of the following piece of code:



class	A{
	public	static void main(String[] args){
		int i = 1;
		int j = 5;
		System.out.println((i++ * j));
		System.out.println("i = " + i + " j = "+ j);
		System.out.println((++i * j));
		System.out.println("i = " + i + " j = " + j);
	}
}

1. Code does not compile
2. Code compiles and prints out



10

I = 2 j=5

15

I = 3 j = 5

3. Code compiles and prints out



5

I = 2 j=5

15

I = 3 j = 5

Answer


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ANSWERS:-

1. b, c

 

 
 
 
 
 
 
 
 
 

Remember, that a compound assignment expression of the form E1 op= E2 is always equivalent to E1 = (Type) (E1 op E2), where Type is the type of E1.

2. b

 

 
 
 
 
 
 
 
 
 

The only modifiers that are allowed with interface methods are public and abstract. And these are implicit, so you don’t even have to include them.

3. a,b,c

 

 
 
 
 
 
 
 
 
 

All three are right. Classes defined within an interface are implicitly public and static and because you cannot have static methods within an iterface, you cannot refer to the non-static methods from the static class methods.

4. a
5. c
6. c, d

 

 
 
 
 
 
 
 
 
 

The only operators that can cause an ArithmeticException are the integer division (/) and modulo (%) operators. Remember that float operations do not raise any exception at all. They may result in NaN or Infinities, instead.

7. -0.0 == 0.0 returns true

 

 
 
 
 
 
 
 
 
 

-0.0 > 0.0 returns false

8. a
9. a, c, d
10. d
11. a, b, d

 

 
 
 
 
 
 
 
 
 

Check out the Java Language Specification for more information on Character Literal and Escape Sequences

12. c

 

 
 
 
 
 
 
 
 
 

Static variables and methods as well as instance variables use the Type of the reference variable to determine the correct variable/method to use. On the other hand, instance methods use the Class of the reference variable to determine the correct method to call

13. b,c,e

 

 
 
 
 
 
 
 
 
 

Unlike methods, a constructor cannot be abstract, static, final, strictfp, native or synchronized.

14. b
15. c
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