Core Java Interview Questions - Part 2

Ans)No. Earlier order is maintained.

Ans) A weak reference is one that does not prevent the referenced object from being garbage collected. You might use them to manage a HashMap to look up a cache of objects. A weak reference is a reference that does not keep the object it refers to alive. A weak reference is not counted as a reference in garbage collection. If the object is not referred to elsewhere as well, it will be garbage collected.

Ans) The code sleep(1000); puts thread aside for exactly one second. The code wait(1000), causes a wait of up to one second. A thread could stop waiting earlier if it receives the notify() or notifyAll() call. The method wait() is defined in the class Object and the method sleep() is defined in the class Thread.

  4) What will be the output on executing the following code.
	public class MyClass {
       public static void main (String args[] ) {
              int abc[] = new int [5];
              System.out.println(abc);
       }
} 

• A Error array not initialized
• B 5
• C null
• D Print some junk characters

Ans) D

It will print some junk characters to the output. Here it will not give any compile time or runtime error because we have declared and initialized the array properly. Event if we are not assigning a value to the array, it will always initialized to its defaults.

  public class MyClass {
       public static void main (String args[] ) {
              int abc[] = new int [5];
              System.out.println(abc[0]);
       }
}

• A Error array not initialized
• B 5
• C 0
• D Print some junk characters

Ans) C. Here it will not give any compile time or runtime error because we have declared and initialized the array properly. Event if we are not assigning a value to the array, it will always initialized to its defaults. So the array will be initialized with values zero.

Ans)An interface that contains no methods. Eg: Serializable, Cloneable, SingleThreadModel etc. It is used to just mark java classes that support certain capability.

Ans)Tag interface is an alternate name for marker interface.

We cannot override static methods. We cannot access any object variables inside static method. Also the this reference also not available in static methods.

Ans)JVM stands for Java Virtual Machine. It is the run time for java programs. All are java programs are running inside this JVM only. It converts java byte code to OS specific commands. In addition to governing the execution of an application's byte codes, the virtual machine handles related tasks such as managing the system's memory, providing security against malicious code, and managing multiple threads of program execution.

Ans)JIT stands for Just In Time compiler. It compiles java byte code to native code.

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