Java 8 Stream findFirst() and findAny()

In Java 8 Stream, the findFirst() returns the first element from a Stream, while findAny() returns any element from a Stream.

1. findFirst()

1.1 Find the first element from a Stream of Integers.

Java8FindFirstExample1.java

package com.favtuts.java8.stream;

import java.util.Arrays;
import java.util.List;
import java.util.Optional;

public class StreamFindExamples {
    
    public static void main(String[] args) {
        demoStreamFindFirst();
    }

    static void demoStreamFindFirst() {
        List<Integer> list = Arrays.asList(1, 2, 3, 2, 1);

        Optional<Integer> first = list.stream().findFirst();
        if (first.isPresent()) {
            Integer result = first.get();
            System.out.println(result);       // 1
        } else {
            System.out.println("no value?");
        }

        Optional<Integer> first2 = list
                .stream()
                .filter(x -> x > 1).findFirst();

        if (first2.isPresent()) {
            System.out.println(first2.get()); // 2
        } else {
            System.out.println("no value?");
        }
    }
}

Output

1
2

1.2 Find the first element from a Stream of String which is not equal to “node”.

Java8FindFirstExample2.java

package com.favtuts.java8.stream;

import java.util.Arrays;
import java.util.List;
import java.util.Optional;

public class StreamFindExamples {
    
    public static void main(String[] args) {
        demoStreamFindFirstAfterFiltering();
    }

    static void demoStreamFindFirstAfterFiltering() {
        List<String> list = Arrays.asList("node", "java", "python", "ruby");

        Optional<String> result = list.stream()
                .filter(x -> !x.equalsIgnoreCase("node"))
                .findFirst();

        if (result.isPresent()) {
            System.out.println(result.get()); // java
        } else {
            System.out.println("no value?");
        }
    }
}

Output

java

2. findAny()

2.1 Find any element from a Stream of Integers. If we run the below program, most of the time, the result is 2, it looks like findAny() always returns the first element? But, there is no guaranteed for this, findAny() may return any element from a Stream.

Java8FindAnyExample1.java

package com.favtuts.java8.stream;

import java.util.Arrays;
import java.util.List;
import java.util.Optional;

public class StreamFindExamples {
    
    public static void main(String[] args) {
        demoStreamFindAny();
    }

    static void demoStreamFindAny() {
        List<Integer> list = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);

        Optional<Integer> any = list.stream().filter(x -> x > 1).findAny();
        if (any.isPresent()) {
            Integer result = any.get();
            System.out.println(result);
        }
    }
}

Output

2 // no guaranteed

Download Source Code

$ git clone https://github.com/favtuts/java-core-tutorials-examples

$ cd java-basic/java8/stream

References

• Java 8 Streams filter examples
• Java 8 Stream JavaDoc
• Stream.findFirst() JavaDoc
• Stream.findAny() JavaDoc