Core Java Interview Questions

Q1: What will be the output of following code?

class Test { Test(int x){ System.out.print("Test("+x+")"); } } class Q1{ static Test t1 =new Test(1); Test t2=new Test(2); static Test t3 = new Test(3); public static void main(String[] args) { Q1 q=new Q1(); } }

now this question for testing the sequence of fields to initialize. Output - Test(1)Test(3)Test(2)

Q2: What will be the output of following code?

byte b =0; while(++b>0) ; System.out.println("Welcome to Java");

Welcome to Java (because in byte, when b=127 and then next iteration it will be -1)

Q3: What will be the output of following code?

if(new Boolean("true")==new Boolean("true")) System.out.println("TRUE"); else System.out.println("FALSE");

FALSE (they are two diffrenent objects)

Q4: What will be the output of following code?

class AA{ static void show(){ System.out.println("A"); } } class B extends AA{ static void show(){ System.out.println("B"); } } class Test { public static void main(String[] args) { AA a=new AA(); a.show(); B b=new B(); b.show(); a=b; a.show(); b=a; b.show(); }}

Answer: b=(B)a Compilation Error

Q5: What will be the output of following code?

class AA{ static void show(){ System.out.println("A"); } } class B extends AA{ void show(){ System.out.println("B"); }}

Answer: Compilation Error (Instance method cannot override the static method from class AA)

Q6: What will be the output of following code?

class AA{ void show(){ System.out.println("A"); } } class B extends AA{ static void show(){ System.out.println("B"); }}

Answer: Compilation Error (static method can not hide the instance method from AA)

Q7: What will be the output of following code?

class Test { public static void main(String[] args) { B b= new B(); b.show(); B.show(); } } class AA{ static void show(){ System.out.println("A"); } } class B extends AA{ }

Output: (You can access static method with subclass reference) A A

Q8: What will be the output of following code?

class Test { static int x=11; public static void main(String[] args) { int x =2; System.out.println(x); }}

Output: 2

Q9: What will be the output of following code?

ArrayList list = new ArrayList(); list.add("B"); list.add("A"); list.add(new Integer(23)); Collections.sort(list);

Answer: Compile but not run. Throw runtime exception – ClassCastException.Collection.sort(List) is used to sort parameterized list. If you comment out list.add(new Integer(23)); then it will run.

Q2: What will be the output of following code?

code code

Welcome to Java (because in byte, when b=127 and then next iteration it will be -1)

Q2: What will be the output of following code?

code code

Welcome to Java (because in byte, when b=127 and then next iteration it will be -1)

Q2: What will be the output of following code?

code code

Welcome to Java (because in byte, when b=127 and then next iteration it will be -1)

Q2: What will be the output of following code?

code code

Welcome to Java (because in byte, when b=127 and then next iteration it will be -1)

Q2: What will be the output of following code?

code code

Welcome to Java (because in byte, when b=127 and then next iteration it will be -1)

Q2: What will be the output of following code?

code code

Welcome to Java (because in byte, when b=127 and then next iteration it will be -1)

Q2: What will be the output of following code?

code code

Welcome to Java (because in byte, when b=127 and then next iteration it will be -1)

Q2: What will be the output of following code?

code code

Welcome to Java (because in byte, when b=127 and then next iteration it will be -1)

Q2: What will be the output of following code?

code code

Welcome to Java (because in byte, when b=127 and then next iteration it will be -1)

Q2: What will be the output of following code?

code code

Welcome to Java (because in byte, when b=127 and then next iteration it will be -1)