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Program: How to get max element of a list of user defined objects using Comparator?


Description:

Collections.min() method returns the minimum element of the given collection, according to the order induced by the specified comparator. All elements in the collection must be mutually comparable by the specified comparator (that is, comp.compare(e1, e2) must not throw a ClassCastException for any elements e1 and e2 in the collection). Below example shows how to get min salary from the given list of user defined objects by using comparator object.


Code:
package com.java2novice.collections;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

public class MyMinComparator {

	public static void main(String a[]){
		
		List<Empy> emps = new ArrayList<Empy>();
		emps.add(new Empy(10, "Raghu", 25000));
		emps.add(new Empy(120, "Krish", 45000));
		emps.add(new Empy(210, "John", 14000));
		emps.add(new Empy(150, "Kishore", 24000));
		Empy minSal = Collections.min(emps, new EmpyComp());
		System.out.println("Employee with min salary: "+minSal);
	}
}

class EmpyComp implements Comparator<Empy>{

	@Override
	public int compare(Empy e1, Empy e2) {
		return e1.getSalary().compareTo(e2.getSalary());
	}
}

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:
Employee with min salary: 210  John   14000
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List Of All Collections Class Sample Programs:

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  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
Purpose of garbage collection
The garbage collection process is to identify the objects which are no longer referenced or needed by a program so that their resources can be reclaimed and reused. These identified objects will be discarded.
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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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