Core Java - Interview Questions and Answers for 'Core Java' | Search Interview Question

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Q1261. Can we initialize final fields within the constructor ? Why ?

Ans. Yes, Because final fields needs to be initialized before the construction of the object completes. Not necessarily at the time of class loading.

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Q1262. When String literals are compared using ==, they always returns true if the string values are same because .. Reference

Core Java

a. of overridden compareTo method

b. of overridden compare method

c. of String Pool

d. == means that the object contents are equal

Ans.c. of String Pool

Q1263. Which of the following is true ?

Core Java

a. Composition is Tightly Bound

b. Inheritance is Tightly Bound

c. Object can only hold reference of only one other object

d. A Class cannot be extended by multiple classes

Ans.b. Inheritance is Tightly Bound

Q1264. In case of String Literals .. Reference

Core Java

a. x==y on all literals always returns false

b. x.equals(y) on all literals always returns false

c. if x.equals(y) returns true, x==y returns true too

d. if x.equals(y) returns false, x==y returns true

Ans.c. if x.equals(y) returns true, x==y returns true too

Q1265. 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

Q1266. 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

Q1267. 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

Q1268. 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

Q1269. What will be the output of following code ?

String str1 = "String1";
String str2 = "String2";
str1.concat("String3");
System.out.print(str1);
System.out.print(str2);

Core Java

a. String1String2

b. String1String3String3

c. String1String3String1String3

d. String1String1

Ans.a. String1String2

Q1270. What will be the output of following code ?

String str1 = "String1";
String str2 = "String2";
str1=str1.concat("String3");
System.out.print(str1);
System.out.print(str2);

Core Java

a. String1String2

b. String1String3String2

c. String1String2String3

d. String1Stringg3String1

Ans.b. String1String3String2

Q1271. 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

Q1272. 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.

Q1273. Collections is a / an ..

Core Java

a. interface

b. abstract class

c. final class

d. util class

Ans.d. util class

Q1274. 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

Q1275. Which of the following can be overridden ? Reference

Core Java

a. final instance methods

b. final static methods

c. non final instance methods

d. non final static methods

Ans.c. non final instance methods

Q1276. 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

Q1277. 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

Q1278. 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();

Q1279. 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();

Q1280. 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();

Q1281. 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

Q1282. 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

Q1283. 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");

Q1284. 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

Q1285. 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

Q1286. 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

Q1287. 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

Q1288. 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

Q1289. 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

Q1290. What will be the ouput upon executing main method ?

public class Vehicle {
   public void move(){
      System.out.println("Vehicle is moving");
   }
}

public class Car {
   public void move(){
      super().move();
      System.out.println("Car is moving");
   }

   public static void main(String[] args){
      new Car().move();
   }
}

Core Java

a. Vehicle is moving

b. Car is moving

c. Vehicle is moving Car is moving

d. Compilation Error

Ans.d. Compilation Error

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