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

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Created by:

ParaEagle

724

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

Edit

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:

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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:

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

2. Minimum

Edit

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:

xxxxxxxxxx
 
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:

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

Example data used in this article

Edit

User.java:

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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 +
                " }";
    }
}
​