Sort list of objects by field in Java 8

The Stream interface includes sorted() method that can be used to sort list of objects by natural order or by using a Comparator.

1) Sort list of objects by natural order using Stream sorted() method

// Stream Sort example    
package java8;

import java.util.Arrays;
import java.util.Comparator;
import java.util.List;

public class StreamSort {

    public static void main(String[] args) {
        List<String> actors = Arrays.asList("Tom", "Harry", "Mark");
        actors.stream().sorted().forEach(System.out::println);
    }
}	

Console Output :

Harry
Mark
Tom	

2) Sort list of objects by providing a Comparable order using Stream sorted() method

In this example we will sort list of Ball objects by name field.

// Stream Sort example    
package java8;

import java.util.Arrays;
import java.util.Comparator;
import java.util.List;

public class StreamSort {

    public static void main(String[] args) {
        Ball tennis = new Ball("tennis", 1, "green");
        Ball footBall = new Ball("football", 2, "white");
        Ball basketBall = new Ball("basketBall", 3, "orange");
        List<Ball> balls = Arrays.asList(tennis, footBall, basketBall);
        balls.stream().sorted().forEach(System.out::println);
    }
}

class Ball implements Comparable<Ball> {

    private String name;
    private int size;
    private String color;

    // removed constructor, getters and setter for brevity    

    @Override
    public String toString() {
        return "Ball [name=" + name + ", size=" + size + ", color=" + color + "]";
    }

    public int compareTo(Ball ball) {
        return this.getName().compareTo(ball.getName());
    }

}	

Console Output :

Ball [name=basketBall, size=3, color=orange]
Ball [name=football, size=2, color=white]
Ball [name=tennis, size=1, color=green]	

3) Sort list of objects by calling Comparator comparing() method using any of the object field.

You can also sort the stream like this

package java8;

import java.util.Arrays;
import java.util.Comparator;
import java.util.List;

public class StreamSort {

    public static void main(String[] args) {
        Ball tennis = new Ball("tennis", 1, "green");
        Ball footBall = new Ball("football", 2, "white");
        Ball basketBall = new Ball("basketBall", 3, "orange");
        List<Ball> balls = Arrays.asList(tennis, footBall, basketBall);
        balls.stream().sorted(Comparator.comparing(Ball::getSize))
            .forEach(System.out::println);
        balls.stream().sorted(Comparator.comparing(Ball::getSize).reversed())
            .forEach(System.out::println);
    }
}
    

Ball [name=tennis, size=1, color=green]
Ball [name=football, size=2, color=white]
Ball [name=basketBall, size=3, color=orange]
Ball [name=basketBall, size=3, color=orange]
Ball [name=football, size=2, color=white]
Ball [name=tennis, size=1, color=green]	

balls.stream().sorted(b1, b2 -> b1.getSize() - b2.getSize())
    .forEach(System.out::println);    

Console Output :