Java Comparator Archives - Huong Dan Java

Sort a Map using Stream and Collectors in Java

In this tutorial, I will show you how to order elements in a Map object using the Stream object and the Collectors object in Java by key and by value. For example, we have a Map object like this:

Map<String, Integer> studentMap = new HashMap<>();
studentMap.put("Khanh", 31);
studentMap.put("Thanh", 25);
studentMap.put("Dung", 35);

Map<String, Integer> studentMap = new HashMap<>();

studentMap.put("Khanh", 31);

studentMap.put("Thanh", 25);

studentMap.put("Dung", 35);

Prior to Java 8, to… Read More

Using Lambda Expression to sort a List in Java

7 years ago by Khanh NguyenJava Basic

Normally, before Java 8, when we want to sort a List object, we will use Comparator object. For example:

package com.huongdanjava.javaexample;

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

public class Example {

	public static void main(String[] args) {
		List<String> names = new ArrayList<>();
		names.add("Thanh");
		names.add("Khanh");
		names.add("Tan");

		Collections.sort(names, new Comparator<String>() {
		    @Override
		    public int compare(String s1, String s2) {
		        return s1.compareTo(s2);
		    }
		});

		for (String s : names) {
			System.out.println(s);
		}
	}
}

package com.huongdanjava.javaexample;

import java.util.ArrayList;

import java.util.Collections;

import java.util.Comparator;

import java.util.List;

public class Example {

public static void main(String[] args) {

List<String> names = new ArrayList<>();

names.add("Thanh");

names.add("Khanh");

names.add("Tan");

Collections.sort(names, new Comparator<String>() {

@Override

public int compare(String s1, String s2) {

return s1.compareTo(s2);

}

});

for (String s : names) {

System.out.println(s);

}

Result: Since Java 8, we have another way to do the sorting a List object. That is: using sort() method in List object with Lambda… Read More