Java Certification Question 0050

Given the following code

public class Sytch{

int x=2000;

public static void main(String argv[]){

System.out.println("Ms "+argv[1]+"Please pay $"+x);

}

}

What will happen if you attempt to compile and run this code with the command line

java Sytch Jones Diggle

1) Compilation and output of Ms Diggle Please pay $2000
2) Compile time error
3) Compilation and output of Ms Jones Please pay $2000
4) Compilation but runtime error

Answer 2:

2) Compile time error

The main method is static and cannot access the non static variable x

Java Certification Question 0049

Which of the following statements are true?

1) The automatic garbage collection of the JVM prevents programs from ever running out of memory
2) A program can suggest that garbage collection be performed but not force it
3) Garbage collection is platform independent
4) An object becomes eligible for garbage collection when all references denoting it are set to null.

Answers 2 and 4:

2) A program can suggest that garbage collection be performed but not force it
4) A reference becomes eligable for garbage collection when it is assigned to null

If a program keeps creating new references without any being discarded it may run out of memory. Unlike most aspects of Java garbage collection is platform dependent.

Java Certification Question 0048

Which of the following statements are true?

1) Static methods cannot be overriden to be non static
2) Static methods cannot be declared as private
3) Private methods cannot be overloaded
4) An overloaded method cannot throw exceptions not checked in the base class

Answer 1:

1) Static methods cannot be overriden to be non static

The JDK1.1 compiler will issue an error message "static methods cannot be overriden" if you atempt to do this. There is no logic or reason why private methods should not be overloaded or that static methods should not be declared private. Option 4 is a jumbled up version of the limitations of exceptions for overriden methods

Java Certification Question 0047

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

class Base{

Base(){

System.out.println("Base");

}

}

public class Checket extends Base{

public static void main(String argv[]){

Checket c = new Checket();

super();

}

Checket(){

System.out.println("Checket");

}

}

1) Compile time error
2) Checket followed by Base
3) Base followed by Checket
4) runtime error

Answer 1:

1) Compile time error

With the sun JDK it will produce the following error

"Only constructors can invoke constructors".

If you took out the call to super that causes this error the program would compile and at runtime it would output Base and then Checket as constructors are called from the oldest ancestor class downwards.

Java Certification Question 0046

Which of the following statements are true?

1) A method cannot be overloaded to be less public in a child class
2) To be overridden a method must have the same name and parameter types
3) To be overridden a method must have the same name, parameter and return types
4) An overridden method must have the same name, parameter names and parameter types

Answer 3:

3) To be overriden a method must have the same name, parameter and return types

Option 1 is a sneaky one in that it should read overriden not overloaded. An overriden method must also have the same return type. Parameter names are purely a programmer convenience and are not a factor in either overloading and overriding. Parameter order is a factor however.