JAVA EXAMPLE PROGRAMS

JAVA EXAMPLE PROGRAMS

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Program: How to create multiple copies of a given object?


Description:

Collections.nCopies() method returns an immutable list consisting of n copies of the specified object. The newly allocated data object is tiny (it contains a single reference to the data object). This method is useful in combination with the List.addAll method to grow lists. The returned list is serializable. Below example shows how to create multiple copies of a user defined object.


Code:
package com.java2novice.collections;

import java.util.Collections;
import java.util.List;

public class MyObjectNCopies {

	public static void main(String a[]){
		
		String temp = "JAVA2NOVICE";
		List<String> tempCopies = Collections.nCopies(5, temp);
		System.out.println(tempCopies);
		Empy emp = new Empy(10, "Raghu", 25000);
		List<Empy> empCopies = Collections.nCopies(5, emp);
		for(Empy e:empCopies){
			System.out.println(e);
		}
	}
}

class Empy{
	
	private int id;
	private String name;
	private Integer salary;
	
	public Empy(int id, String name, Integer sal){
		this.id = id;
		this.name = name;
		this.salary = sal;
	}
	
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public Integer getSalary() {
		return salary;
	}
	public void setSalary(Integer salary) {
		this.salary = salary;
	}
	public String toString(){
		return id+"  "+name+"   "+salary;
	}
}

Output:
[JAVA2NOVICE, JAVA2NOVICE, JAVA2NOVICE, JAVA2NOVICE, JAVA2NOVICE]
10  Raghu   25000
10  Raghu   25000
10  Raghu   25000
10  Raghu   25000
10  Raghu   25000
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List Of All Collections Class Sample Programs:

  1. How to add all elements to the given collection object?
  2. Write an example for Collections.asLifoQueue() method.
  3. How to search user defined object from a List by using binary search?
  4. Write an example for Collections.checkedCollection() method.
  5. Write an example for Collections.checkedList() method.
  6. Write an example for Collections.checkedSet() method.
  7. Write an example for Collections.checkedMap() method.
  8. How to check there in no common element between two list objects by using Collections.disjoint() method?
  9. How to create empty list using Collections class?
  10. How to create empty set using Collections class?
  11. How to create empty map using Collections class?
  12. How to Enumeration for ArrayList object?
  13. How to fill or replace elements of a List or ArrayList?
  14. How to find repeated element cound (frequency) of a given collection?
  15. How to convert Enumeration to List object?
  16. How to get index of a sub list from another list?
  17. How to get last index of a sub list from another list?
  18. How to get max element from the given list?
  19. How to get min element from the given list?
  20. How to get max element of a list of user defined objects?
  21. How to get min element of a list of user defined objects?
  22. How to get max element of a list of user defined objects using Comparator?
  23. How to get min element of a list of user defined objects using Comparator?
  24. How to create multiple copies of a given object?
  25. How to replace all occurances of a given object in the list?
  26. How to rotate elements in the list by specified distance?
  27. How to create synchronized list?
  28. How to create synchronized set?
  29. How to create synchronized map?
Knowledge Centre
Where can we use serialization?
Whenever an object has to sent over the network, those objects should be serialized. Also if the state of an object is to be saved, objects need to be serilazed.
Famous Quotations
When I do good, I feel good; when I do bad, I feel bad, and that is my religion.
-- Abraham Lincoln

About Author

I'm Nataraja Gootooru, programmer by profession and passionate about technologies. All examples given here are as simple as possible to help beginners. The source code is compiled and tested in my dev environment.

If you come across any mistakes or bugs, please email me to [email protected].

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Reference: Java™ Platform Standard Ed. 7 - API Specification | Java™ Platform Standard Ed. 8 - API Specification | Java is registered trademark of Oracle.
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