Stream allMatch() in Java with examples

The allMatch() method in Java Streams is a terminal operation that returns true if all elements of the stream match the given predicate, or if the stream is empty. It is short-circuiting, meaning it may stop evaluating elements as soon as the result is determined.

Example:

Java

import java.util.stream.Stream;
class GFG {
    public static void main(String[] args) {
        Stream<Integer> numbers = Stream.of(2, 4, 6, 8);
        boolean result = numbers.allMatch(n -> n % 2 == 0);
        System.out.println(result);
    }
}

Output

true

Explanation:

A stream of integers 2, 4, 6, 8 is created using Stream.of().
The allMatch(n -> n % 2 == 0) method checks whether all numbers are even.
Since all elements satisfy the condition, it returns true.
The result is printed to the console.

Syntax

boolean allMatch(Predicate<? super T> predicate)

Parameters: "predicate" a functional interface representing a condition to test each element.
Return Value: Returns true if all elements match the predicate or the stream is empty.

Example 1: This program uses allMatch() to check if all elements in a stream of numbers are divisible by 3.

Java

import java.util.stream.Stream;
class GFG {
    public static void main(String[] args) {
        Stream<Integer> numbers = Stream.of(3, 6, 9, 10);
        boolean result = numbers.allMatch(n -> n % 3 == 0);
        System.out.println(result);
    }
}

Output

false

Explanation:

A stream of integers 3, 6, 9, 10 is created using Stream.of().
The allMatch(n -> n % 3 == 0) method checks whether each number is divisible by 3.
Since 10 is not divisible by 3, the method returns false.

Example 2: This program uses allMatch() to check if all strings in a stream have length greater than 2.

Java

import java.util.stream.Stream;
class GFG {
    public static void main(String[] args) {
        Stream<String> strings = Stream.of("Java", "GFG", "Stream");
        boolean result = strings.allMatch(s -> s.length() > 2);
        System.out.println(result);
    }
}

Output

true

Explanation:

A stream of strings "Java", "GFG", "Stream" is created using Stream.of().
The allMatch(s -> s.length() > 2) method checks whether each string has more than 2 characters.
Since all strings satisfy the condition, it returns true.

Example 3: This program uses allMatch() to check if all strings in a stream start with an uppercase character.

Java

import java.util.stream.Stream;
class GFG {
    public static void main(String[] args) {
        Stream<String> strings = Stream.of("Java", "gFG", "Stream");
        boolean result = strings.allMatch(s -> Character.isUpperCase(s.charAt(0)));
        System.out.println(result);
    }
}

Output

false

Explanation:

A stream of strings "Java", "gFG", "Stream" is created using Stream.of().
The allMatch(s -> Character.isUpperCase(s.charAt(0))) method checks whether the first character of each string is uppercase.
Since "gFG" starts with a lowercase letter, the method returns false.

Example 4: This program demonstrates that a stream cannot be reused after a terminal operation like allMatch().

Java

import java.util.stream.Stream;

class GFG {
    public static void main(String[] args) {
        Stream<String> strings = Stream.of("Java", "GFG", "Stream");
        boolean res1 = strings.allMatch(s -> s.length() > 2);
        // Uncommenting the next line will throw IllegalStateException because the stream 
        // is already consumed
        // boolean res2 = strings.allMatch(s -> Character.isUpperCase(s.charAt(0)));
        
        System.out.println(res1);
        // System.out.println(res2);
    }
}

Output

true

Explanation:

A stream of strings "Java", "GFG", "Stream" is created using Stream.of().
The first terminal operation allMatch(s -> s.length() > 2) checks whether all strings have length greater than 2 and returns true.
Attempting to use the same stream again (commented res2) would throw IllegalStateException because streams can be consumed only once.
The result of the first operation is printed.

Stream allMatch() in Java with examples

Syntax

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