Interview Questions and Answers for 'T' | Search Interview Question

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Q2611. Can a lock be acquired on a class? How is it different than the object level lock ?

Ans. Yes, a lock can be acquired on the class. Class level lock is applicable on the whole class and hence on all objects of the class whereas the object level lock is applicable on the respective object.

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Q2612. Difference between Yielding and Sleeping ?

Ans. When a task invokes its yield method, it returns to the ready state. When a task invokes its sleep method, it returns to the waiting state.

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Q2613. What is the use of Runtime Class ?

Ans. This class is used to provide access to the Java runtime system

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Frequently asked.

Q2614. What should a class do if its implementing an interface ?

Core Java

Ans. It should either implement all interface methods or declare unimplemented methods as abstract.

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Q2615. What should a class do if its extending an abstract class ?

Core Java

Ans. It should either implement the abstract methods or re-declare them abstract.

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Q2616. What is a compilation unit in Java ?

Ans. Java Source Code File

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Q2617. What is Associativity while evaluating a Java statement ?

Core Java

Ans. Associativity determines whether an expression is evaluated left-right or right-left. When an expression has two operators with the same precedence, the expression is evaluated according to its associativity.

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Q2618. What is a package and what are its advantages ?

Core Java

Ans. Package is a namespace that organizes a set of related classes.

Advantages of Packages

1. Better Organization of classes.
2. Saves from the problem of duplicate names as duplicate class names are allowed across different packages.

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Q2619. What is a default constructor ? Reference

Core Java

a. Constructor without parameters declared by user

b. Constructor provided by Java if no constructor is declared

c. Constructor with empty body

d. All of the above

Ans.b. Constructor provided by Java if no constructor is declared

Q2620. How can we create objects if we make the constructor private ?

Core Java

a. We can't create objects if constructor is private

b. We can only create objects if we follow singleton pattern

c. We can only create one object

d. We can create new object through static method or static block

Ans.d. We can create new object through static method or static block

Q2621. What will be the output of following ?

String str1 = new String("String1");
String str2 = new String("String1");
System.out.print(str1 == str2);
System.out.print(str1.equals(str2));
str1 = str2;
System.out.print(str1 == str2);

Core Java

a. falsetruetrue

b. truetruetrue

c. truetruefalse

d. falsetruefalse

Ans.a. falsetruetrue

Q2622. What will be the output of following code ?

String str1 = "String1";
String str2 = "String1";
System.out.print(str1 == str2);
System.out.print(str1.equals(str2));
str1 = str2;
System.out.print(str1 == str2);

Core Java

a. falsetruetrue

b. falsefalsetrue

c. truetruetrue

d. falsefalsefalse

Ans.c. truetruetrue

Q2623. Which method needs to be implemented if a class is implementing comparable interface ?

Core Java

a. comp

b. compare

c. compareTo

d. compareEquals

Ans.c. compareTo

Q2624. Which of the following is false ?

Core Java

a. A Class cannot override both hashcode and equals method.

b. A class can override both hashcode and equals method.

c. A Class must override hashCode method if its overridding equal method.

d. A Class can override hashCode even if its not overridding equals method.

Ans.a. A Class cannot override both hashcode and equals method.

Q2625. Collections is a / an ..

Core Java

a. interface

b. abstract class

c. final class

d. util class

Ans.d. util class

Q2626. Which of the following can throw ClassCastException ?

Core Java

a. UpCasting

b. DownCasting

c. Casting to incompatible data type

d. Casting to Strings

Ans.b. DownCasting

Q2627. x instanceOf y returns false ..

Core Java

a. if x is an instance of y class

b. if x is an instance of class implementing y interface

c. if x is an instance of class extending y class

d. if x is an instance of Class which is a parent of Y class

Ans.d. if x is an instance of Class which is a parent of Y class

Q2628. notify(), notifyAll(), wait() are found in which class Reference

Core Java

a. java.lang.Object

b. java.lang.Thread

c. java.lang.Runnable

d. java.lang.Implement

Ans.a. java.lang.Object

Q2629. if classes B and C extends Class A, Which of the following initialization is correct ?

Core Java

a. B b = new C();

b. C c = new B();

c. B b = new A();

d. A a = new B();

Ans.d. A a = new B();

Q2630. If X implements Y and Y extends Z, Which of the following initialization is correct ?

Core Java

a. X x = new Y();

b. X x = new Z();

c. Z z = new Y();

d. Z z = new X();

Ans.d. Z z = new X();

Q2631. If class A implements X interface, and Class B implements Y interface, and X is the parent of Y, Which of the following initialization is correct ?

Core Java

a. A a = new B();

b. Y y = new A();

c. X x = new B();

d. Y y = new A();

Ans.c. X x = new B();

Q2632. What will be the output of executing following class ?

public class BuggyBread {

static {
System.out.println("Static Block");
}

{
System.out.println("Initialization Block");
}

BuggyBread(){
System.out.println("Constructor");
}

public static void main(String[] args){
System.out.println("Main Method");
}
}

Core Java

a. Static Block
Main Method

b. Static Block
Instance Initialization Block
Main Method

c. Static Block
Constructor
Main Method

d. Static Block
Instance Initialization Block
Constructor
Main Method

Ans.a. Static Block
Main Method

Q2633. What will be the output upon executing following class ?

public class BuggyBread {

static {
System.out.println("Static Block");
}

{
System.out.println("Instance Initialization Block");
}

BuggyBread(){
System.out.println("Constructor");
}

public static void main(String[] args){
System.out.println("Main Method");
new BuggyBread();
}
}

Core Java

a. Instance Initialization Block
Constructor
Static Block
Main Method

b. Static Block
Instance Initialization Block
Constructor
Main Method

c. Main Method
Static Block
Instance Initialization Block
Constructor

d. Static Block
Main Method
Instance Initialization Block
Constructor

Ans.d. Static Block
Main Method
Instance Initialization Block
Constructor

Q2634. With the following code, Which is a valid way to initialize ?
public class BuggyBread {

   private String element1;

   private String element2;

   private BuggyBread(String element1, String element2){
      this.element1 = element1;
      this.element2 = element2;
   }

   public static class Builder {

      private String element1;

      private String element2;

      Builder(BuggyBread buggybread){
         element1 = buggybread.element1;
         element2 = buggybread.element2;
      }

      Builder withElement1(String element1){
         this.element1 = element1;
         return this;
      }

      Builder withElement2(String element2){
         this.element2 = element2;
         return this;
      }

      BuggyBread build(){
         BuggyBread buggybread = new BuggyBread(element1,element2);
         return buggybread;
      }
   }
}

Core Java

a. BuggyBread buggybread = new BuggyBread();

b. BuggyBread buggybread = new BuggyBread("element1","element2");

c. BuggyBread.Builder builder = new BuggyBread.Builder();

d. BuggyBread.Builder builder = new BuggyBread.Builder("element1","element2");

Ans.d. BuggyBread.Builder builder = new BuggyBread.Builder("element1","element2");

Q2635. What will be the output of following code ?

public class BuggyBread {

   private int x;
   private int y;

   BuggyBread(int x,int y){};

   public static void main(String[] args){
      BuggyBread buggybread = new BuggyBread();
      System.out.println(buggybread.x);
   }
}    Reference

Core Java

a. 0

b. null

c. compilation error due to uninitialized element

d. compilation error due to constructor

Ans.d. compilation error due to constructor

Q2636. What will be the output of following ?

public class BuggyBread {

   private int x;
   private Integer y;

   BuggyBread(int x,int y){};

   public static void main(String[] args){
      BuggyBread buggybread = new BuggyBread(1,2);
      System.out.println(buggybread.x);
      System.out.println(buggybread.y);
   }
}    Reference

Core Java

a. 0 0

b. 0 null

c. null 0

d. null null

Ans.b. 0 null

Q2637. What will be the output of following code ?

public class BuggyBread {

   private int x;
   private Integer y;

   private BuggyBread(int x,int y){};

   public static void main(String[] args){
      BuggyBread buggybread = new BuggyBread(1,2);
      System.out.println(buggybread.x);
   }
}

Core Java

a. compilation error due to private constructor

b. compilation error due to uninitialized elements

c. 0 null

d. 0 0

Ans.c. 0 null

Q2638. What will be the output of following code ?

public class BuggyBread {

   private int x;

   private BuggyBread(int x){
      x = x;
   };

   public static void main(String[] args){
      BuggyBread buggybread = new BuggyBread(5);
      System.out.println(buggybread.x);
   }
}

Core Java

a. compilation error

b. undefined

c. 0

d. 5

Ans.c. 0

Q2639. What will be the output of exceuting main method ?

public static void main(String[] args){
      List list = new ArrayList();
      list.add(1);
      list.add(2);
      list.add(3);
      System.out.println(list);
   }

Core Java

a. 1,2,3

b. Order cannot be determined

c. compilation error

d. 3,2,1

Ans.a. 1,2,3

Q2640. What will be the output upon executing main method ?

public static void main(String[] args){
      Set set = new HashSet();
      set.add(1);
      set.add(2);
      set.add(3);
      System.out.println(set);
   }

Core Java

a. 1,2,3

b. Order cannot be determined

c. Compilation error

d. 3,2,1

Ans.b. Order cannot be determined

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