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Java 8 - find max and min value in List of objects

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Created by:
ParaEagle
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In this article, we would like to show you how to find maximum and minimum values in a list of custom objects in Java 8.

 

1. Maximum

In this example, we use:

  • stream() - to get a stream of values from the users list,
  • max() method on the stream - to get the maximum value
    • we are passing a custom comparator¬†that specifies¬†the sorting logic when determining the maximum value,
  • orElseThrow()¬†- to throw an exception if no value is received from max() method.

Practical example:

import java.io.IOException;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.List;
import java.util.NoSuchElementException;


public class Example {

    public static void main(String[] args) throws IOException {

        User user1 = new User("Tom", 20);
        User user2 = new User("Kate", 21);
        User user3 = new User("Ann", 22);

        List<User> users = new ArrayList<>();

        users.add(user1);
        users.add(user2);
        users.add(user3);

        User maxAge = users
                .stream()
                .max(Comparator.comparing(User::getAge))
                .orElseThrow(NoSuchElementException::new);

        System.out.println(maxAge);
    }
}

Output:

User{ name='Ann', age=22 }

2. Minimum

In this example, we use:

  • stream() - to get a stream of values from the users list,
  • min() method on the stream - to get the minimum value
    • we are passing a custom comparator¬†that specifies¬†the sorting logic when determining the minimum value.
  • orElseThrow()¬†- to throw an exception if no value is received from min() method.

Practical example:

import java.io.IOException;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.List;
import java.util.NoSuchElementException;


public class Example {

    public static void main(String[] args) throws IOException {

        User user1 = new User("Tom", 20);
        User user2 = new User("Kate", 21);
        User user3 = new User("Ann", 22);

        List<User> users = new ArrayList<>();

        users.add(user1);
        users.add(user2);
        users.add(user3);

        User minAge = users
                .stream()
                .min(Comparator.comparing(User::getAge))
                .orElseThrow(NoSuchElementException::new);

        System.out.println(minAge);
    }
}

Output:

User{ name='Tom', age=20 }

Example data used in this article

User.java:

public class User {
    private final String name;
    private final int age;

    public User(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }

    @Override
    public String toString() {
        return "User{ " +
                "name='" + name + '\'' +
                ", age=" + age +
                " }";
    }
}
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