Showing posts with label custom sort by key or value hash map. Show all posts
Showing posts with label custom sort by key or value hash map. Show all posts

Saturday, September 24, 2016

How to do customized Sorting byHashMap key or by value using Comparator - Java


This post will explain how to sort by key and sort by value using HashMap and Comparator.

Step 1: First create a Employee class which is having all the details related to Employee

/**
 * 
 * @author rajusiva
 *
 */

public class Employee {

	
	Integer empId;
	String name;
	Float salary;
	
	public Employee(Integer id,String name, Float sal){
		this.empId = id;
		this.name = name;
		this.salary = sal;
		
	}
	
	@Override
	public String toString() {
		return "Emp Id: "+this.empId+" Name: "+this.name +" salary: " +this.salary;
	}

	public Integer getEmpId() {
		return empId;
	}
	public void setEmpId(Integer empId) {
		this.empId = empId;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public Float getSalary() {
		return salary;
	}
	public void setSalary(Float salary) {
		this.salary = salary;
	}

}


Step 2: Below is the class for sort by key and sort by value using comparator
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.TreeMap;

/** This class is used to custom sort using Comparator interface and overriding compare method.
 * 
 * @author rajusiva
 *
 */
public class CustomHashMapSort {
	
	public static void main(String[] args) {
		Map map = new HashMap();
		map.put("205", new Employee(1, "siva", 75000f));
		map.put("202", new Employee(2, "raju", 85000f));
		map.put("203", new Employee(3, "kumar", 50000f));
		map.put("204", new Employee(4, "arjun", 35000f));
		map.put("200", new Employee(5, "neha", 45000f));
		map.put("198", new Employee(6, "sneha", 25000f));
		
		Map sortedMap = new TreeMap(map);
		for (Iterator iterator = sortedMap.keySet().iterator(); iterator.hasNext();) {
			String key = (String) iterator.next();
			Employee emp = map.get(key);
			System.out.println("Sort By key [" + key  +"]  [" + emp + "]");
			
		}
		System.out.println("=============================================");
		HashMap sortedMapByValue = sortByValue(map);
		for (Iterator iterator = sortedMapByValue.keySet().iterator(); iterator.hasNext();) {
			String key = (String) iterator.next();
			Employee emp = map.get(key);
			System.out.println("Sort By Value by Name  Key-[ "+key  +"]  value [" + emp.getName() +"]");
			
		}
		
		
	}
	/**This method will used to sort custom object value type(either empId,name, salary)
	 * 
	 * @param empLoyeeMap of type Map values
	 * @return sorted hashmap values
	 */
	public static  HashMap sortByValue(Map empLoyeeMap) {
		List> list = new java.util.LinkedList>(empLoyeeMap.entrySet());

		Collections.sort(list, new Comparator>() {
        // sort the value using compare method and comparator
		 @Override
		 public int compare(Map.Entry value1, Map.Entry value2) {
		 return (value1.getValue().getName()).compareTo(value2.getValue().getName());
		 }
		});
		
		 HashMap sortedHashMap = new LinkedHashMap();
	       for (Iterator it = list.iterator(); it.hasNext();) {
	              Map.Entry entry = (Map.Entry) it.next();
	              sortedHashMap.put(entry.getKey(), entry.getValue());
	       } 
	       return sortedHashMap;
		
		
	}
	

}


output:

Sort By key [198]  [Emp Id: 6 Name: sneha salary: 25000.0]
Sort By key [200]  [Emp Id: 5 Name: neha salary: 45000.0]
Sort By key [202]  [Emp Id: 2 Name: raju salary: 85000.0]
Sort By key [203]  [Emp Id: 3 Name: kumar salary: 50000.0]
Sort By key [204]  [Emp Id: 4 Name: arjun salary: 35000.0]
Sort By key [205]  [Emp Id: 1 Name: siva salary: 75000.0]
=============================================
Sort By Value by Name  Key-[ 204]  value [arjun]
Sort By Value by Name  Key-[ 203]  value [kumar]
Sort By Value by Name  Key-[ 200]  value [neha]
Sort By Value by Name  Key-[ 202]  value [raju]
Sort By Value by Name  Key-[ 205]  value [siva]
Sort By Value by Name  Key-[ 198]  value [sneha]


Hope this will help you to understand how we can custom object sort by key and value using comparator.


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