Remove all elements from hashtable java example

Posted by: Instanceofjava Posted date: March 16, 2016 / comment : 0 ,

1.Basic java example program to remove all elements from hashtable
  • Object remove(Object key)    This method used to remove value pair from hashtable
  • void clear() this method removes all elements from hashtable
  •  
  1. package com.removevalueHashtable;
  2.  
  3. import java.util.Hashtable;

  5. import java.util.Enumeration;
  6.  
  7. public class HashtableExample{
  8.  
  9. public static void main(String[] args) {
  10.   
  11.  //create Hashtable object
  12.        Hashtable<String,String> hashtable = new Hashtable<String,String>();
  13.        
  14. //add key value pairs to Hashtable
  15. hashtable.put("1","Java Interview Questions");
  16. hashtable.put("2","Java Interview Programs");
  17. hashtable.put("3","Concept and example program");
  18. hashtable.put("4","Concept and interview Questions");
  19. hashtable.put("5","Java Quiz");
  20. hashtable.put("6","Real time examples");
  21.  
  22. Object obj = ht.remove("2");
  23. System.out.println(obj + " Removed from Hashtable");
  24.  
  25. Enumeration e=hashtable.elements();
  26.           
  27.  
  28.  while (e.hasMoreElements()) {
  29.         System.out.println(e.nextElement());
  30. }    
  31. hashtable.clear();
  32.  
  33.  System.out.println("Total key value pairs in Hashtable are : " + hashtable.size());

  35. }
  36.  
  37. }
     



Output:

  1. Java Interview Programs Removed from Hashtable
  2. Real time examples
  3. Java Quiz
  4. Concept and interview Questions
  5. Concept and exampe program
  6. Java Interview Questions
  7. Total key value pairs in Hashtable are : 0

Remove key value pair from hashtable java example

Posted by: Instanceofjava Posted date: March 16, 2016 / comment : 0 ,

1.Basic java example program to iterate keys of hashtable
  • Object remove(Object key)    This method used to remove value pair from hashtable
  1. package com.removevalueHashtable;
  2.  
  3. import java.util.Hashtable;

  5. import java.util.Enumeration;
  6.  
  7. public class HashtableExample{
  8.  
  9. public static void main(String[] args) {
  10.   
  11.  //create Hashtable object
  12.        Hashtable<String,String> hashtable = new Hashtable<String,String>();
  13.        
  14. //add key value pairs to Hashtable
  15. hashtable.put("1","Java Interview Questions");
  16. hashtable.put("2","Java Interview Programs");
  17. hashtable.put("3","Concept and example program");
  18. hashtable.put("4","Concept and interview Questions");
  19. hashtable.put("5","Java Quiz");
  20. hashtable.put("6","Real time examples");
  21.  
  22. Object obj = ht.remove("2");
  23. System.out.println(obj + " Removed from Hashtable");
  24.  
  25. Enumeration e=hashtable.elements();
  26.           
  27.  
  28.            
  29. // display search result
  30.  while (e.hasMoreElements()) {
  31.         System.out.println(e.nextElement());
  32. }    

  34. }
  35.  
  36. }
     



Output:

  1. Java Interview Programs Removed from Hashtable
  2. Real time examples
  3. Java Quiz
  4. Concept and interview Questions
  5. Concept and exampe program
  6. Java Interview Questions

Iterate through values of hashtable java

Posted by: Instanceofjava Posted date: March 16, 2016 / comment : 0 ,

1.Basic java example program to iterate keys of hashtable
  • Enumeration elements()   This method used to get values of hashmap

  1. package com.iteartekeysHashtable;
  2.  
  3. import java.util.Hashtable;

  5. import java.util.Enumeration;
  6.  
  7. public class HashtableExample{
  8.  
  9. public static void main(String[] args) {
  10.   
  11.  //create Hashtable object
  12.        Hashtable<String,String> hashtable = new Hashtable<String,String>();
  13.        
  14. //add key value pairs to Hashtable
  15. hashtable.put("1","Java Interview Questions");
  16. hashtable.put("2","Java Interview Programs");
  17. hashtable.put("3","Concept and example program");
  18. hashtable.put("4","Concept and interview Questions");
  19. hashtable.put("5","Java Quiz");
  20. hashtable.put("6","Real time examples");
  21.  
  22.  
  23.  
  24. Enumeration e=hashtable.elements();
  25.           
  26.  
  27.            
  28. // display search result
  29.  while (e.hasMoreElements()) {
  30.         System.out.println(e.nextElement());
  31. }    

  33. }
  34.  
  35. }
     



Output:

  1. Real time examples
  2. Java Quiz
  3. Concept and interview Questions
  4. Concept and example program
  5. Java Interview Programs
  6. Java Interview Questions

Method overloading interview questions java

Posted by: Instanceofjava Posted date: March 16, 2016 / comment : 0

1.What is Method in java?

  • Method is a sub block of a class that contains logic of that class.
  • logic must be placed inside a method, not directly at class level, if we place logic at class level compiler throws an error.
  • So class level we are allowed to place variables and methods.
  • The logical statements such as method calls, calculations and printing related statements must be placed inside method, because these statements are considered as logic. 
  • For more information @ Methods in java



  1. package com.instanceofjava;
  2. class sample{
  3.  
  4. int a;
  5. int b;
  6.  
  7. System.out.println("instance of java"); // compiler throws an error.
  8.  
  9. }
  10.  

  1. package com.instanceofjava;
  2. class sample{
  3.  
  4. static int a=10;
  6.    
  7. public static void main(String args[]){

  9. System.out.println(a); // works fine,prints a value:10
  10.  
  11.  }
  12. }

2.What is meant by method overloading in java?


  • Defining multiple methods with same name is known as polymorphism.
  • Defining multiple methods with same name and with different arguments known as method overloading.

  1. package com.instanceofjava;
  2. class A{
  3.  
  4. public void show(int a){
  5. System.out.println("saidesh");
  6. }
  7.  
  8. public void show(int a,int b){
  9. System.out.println("ajay");
  10. }
  11.  
  12. public void show(float a){
  13. System.out.println("vinod");
  14. }
  15. public static void main(String args[]){
  16.  
  17. A a=new A();
  18.  
  19. a.show(10);
  20. a.show(1,2);
  21. a.show(1.2);
  22.  
  23. }
  24. }
Output:

  1. saidesh
  2. ajay
  3. vinod


3.What are the other names for method overloading?


  • Method overloading also known as static polymorphism or compile time polymorphism because at compile time itself we can tell which method going to get executed based on method arguments.
  • So method overloading also called as static binding. 

4.What are the basic rules of method overloading?

  • Defining a method with same name and differ in number of arguments
  • Defining a method with same name and differ in type of arguments
  • Defining a method with same name and differ in order of type of arguments
  • Return type of the method not involved in method overloading.

5.Can we overload static methods in java?

  • Yes. We can overload static methods in java.
  • Method overriding is not possible but method overloading is possible for static methods.
  • Before that lets see about method overloading in java.
  • lets see an example java program which explains static method overloading.
  1. class StaticMethodOverloading{
  2.  
  3. public static void staticMethod(){
  4.  
  5. System.out.println("staticMethod(): Zero arguments");
  6.  
  7. } 
  8.  
  9. public static void staticMethod(int a){
  10.  
  11. System.out.println("staticMethod(int a): one argument");
  12.  
  13. } 
  14.  
  15. public static void staticMethod(String str, int x){
  16.  
  17. System.out.println("staticMethod(String str, int x): two arguments");
  18.  
  19. }
  20.  
  21. public static void main(String []args){
  22.   
  23.   StaticMethodOverloading.staticMethod();
  24.   StaticMethodOverloading.staticMethod(12);
  25.   StaticMethodOverloading.staticMethod("Static method overloading",10);
  26.  
  27. }
  28. }


 Output:

  1. staticMethod(): Zero arguments
  2. staticMethod(int a): one argument
  3. staticMethod(String str, int x): two arguments


6.Can we overload main method in java?

Yes we can overload main method in java

Java Program to overload main method in java

  1. class mainMethodOverloading{
  2.  
  3. public static void main(boolean x){
  4.  
  5. System.out.println("main(boolean x) called ");
  6.  
  7. } 
  8.  
  9. public static void main(int x){
  10.  
  11. System.out.println("main(int x) called");
  12.  
  13. } 
  14.  
  15. public static void main(int a, int b){
  16.  
  17. System.out.println("main(int a, int b) called");
  18.  
  19. }
  20.  
  21. public static void main(String []args){
  22.    
  23.  
  24. System.out.println("main(String []args) called ");
  25.  
  26.   mainMethodOverloading.main(true);
  27.   mainMethodOverloading.main(10);
  28.  mainMethodOverloading.main(37,46);
  29.  
  30.  
  31. }
  32. }




 Output:

  1. main(String []args) called
  2. main(boolean x) called
  3. main(int x) called
  4. main(int a, int b) called

method overloading interview questions





7.Can we overload constructors in java?

  • Yes we can overload constructor in java

  1. package instanceofjava;
  2. class ConstructorChaining{
  3. int a,b 
  4. ConstructorChaining(){
  5. this(1,2);
  6.  System.out.println("Default constructor");
  7.  
  8. } 
  9.  
  10. ConstructorChaining(int x , int y){
  11.  
  12. this(1,2,3); 
  13. a=x;
  14. b=y;
  15.  System.out.println("Two argument constructor");
  16.  
  17. }
  18.  
  19. ConstructorChaining(int a , int b,int c){
  20.  System.out.println("Three argument constructor")
  21. } 
  22.  
  23. public static void main(String[] args){
  24.  
  25.  ConstructorChaining obj=new ConstructorChaining();
  26.   System.out.println(obj.a);
  27.   System.out.println(obj.b);
  28.  
  29. }
  30. }


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Iterate through keys of hashtable java

Posted by: Instanceofjava Posted date: March 16, 2016 / comment : 0 ,

1.Basic java example program to iterate keys of hashtable
  • Enumeration keys()   This method used to get keys of hashmap

  1. package com.iteartekeysHashtable;
  2.  
  3. import java.util.Hashtable;

  5. import java.util.Enumeration;
  6.  
  7. public class HashtableExample{
  8.  
  9. public static void main(String[] args) {
  10.   
  11.  //create Hashtable object
  12.        Hashtable<String,String> hashtable = new Hashtable<String,String>();
  13.        
  14. //add key value pairs to Hashtable
  15. hashtable.put("1","Java Interview Questions");
  16. hashtable.put("2","Java Interview Programs");
  17. hashtable.put("3","Concept and exampe program");
  18. hashtable.put("4","Concept and interview Questions");
  19. hashtable.put("5","Java Quiz");
  20. hashtable.put("6","Real time examples");
  21.  
  22.  
  23.  
  24. Enumeration e=hashtable.keys();
  25.           
  26.  
  27.            
  28. // display search result
  29.  while (e.hasMoreElements()) {
  30.         System.out.println(e.nextElement());
  31. }    

  33. }
  34.  
  35. }
     



Output:

  1. 6
  2. 5
  3. 4
  4. 3
  5. 2
  6. 1

Check particular value exist in hashtable

Posted by: Instanceofjava Posted date: March 16, 2016 / comment : 0 ,

1.Basic java example program to check particular value exist in hashtable
  • boolean contains(Object value)   This method used to check  particular value exist in hashtable

  1. package com.CheckElelemtHashtable;
  2.  
  3. import java.util.Hashtable;

  5. import java.util.Enumeration;
  6.  
  7. public class HashtableExample{
  8.  
  9. public static void main(String[] args) {
  10.   
  11.  //create Hashtable object
  12.        Hashtable<String,String> hashtable = new Hashtable<String,String>();
  13.        
  14. //add key value pairs to Hashtable
  15. hashtable.put("1","Java Interview Questions");
  16. hashtable.put("2","Java Interview Programs");
  17. hashtable.put("3","Concept and exampe program");
  18. hashtable.put("4","Concept and interview Questions");
  19. hashtable.put("5","Java Quiz");
  20. hashtable.put("6","Real time examples");
  21.  
  22.  /*
  23.  To check whether a particular value exists in Hashtable we need to use
  24.  boolean containsKey(Object value) method of Hashtable class.
  25. if the Hashtable contains mapping for specified value It returns true
  26. otherwise returns false.
  27. */
  28.        
  29.  boolean isExists = hashtable.contains("Java Quiz");
  30.  System.out.println("Java Quiz exists in Hashtable ? : " + isExists);

  32. System.out.println("Hashtable values : ");
  33.  
  34. Enumeration e=hashtable.elements();
  35.           
  36.  
  37.            
  38. // display search result
  39.  while (e.hasMoreElements()) {
  40.         System.out.println(e.nextElement());
  41. }    

  43. }
  44.  
  45. }
     



Output:

  1. Java Quiz exists in Hashtable ? : true
  2. Hashtable values : 
  3. Real time examples
  4. Java Quiz
  5. Concept and interview Questions
  6. Concept and exampe program
  7. Java Interview Programs
  8. Java Interview Questions
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