Stream filter() in Java with examples

Stream filter(Predicate predicate) returns a stream consisting of the elements of this stream that match the given predicate. This is an intermediate operation. These operations are always lazy i.e, executing an intermediate operation such as filter() does not actually perform any filtering, but instead creates a new stream that, when traversed, contains the elements of the initial stream that match the given predicate.

Syntax :

Stream<T> filter(Predicate<? super T> predicate)

Where, Stream is an interface and T is the 
type of the input to the predicate.
The function returns the new stream.

Example 1 : filter() method with operation of filtering out the elements divisible by 5.

// Java code for Stream filter 
// (Predicate predicate) to get a stream 
// consisting of the elements of this 
// stream that match the given predicate. 
import java.util.*; 
  
class GFG { 
  
    // Driver code 
    public static void main(String[] args) 
    { 
  
        // Creating a list of Integers 
        List<Integer> list = Arrays.asList(3, 4, 6, 12, 20); 
  
        // Using Stream filter(Predicate predicate) 
        // to get a stream consisting of the 
        // elements that are divisible by 5 
        list.stream().filter(num -> num % 5 == 0).forEach(System.out::println); 
    } 
} 

Output :

Example 2 : filter() method with operation of filtering out the elements with upperCase letter at index 1.

// Java code for Stream filter 
// (Predicate predicate) to get a stream 
// consisting of the elements of this 
// stream that match the given predicate. 
import java.util.stream.Stream; 
  
class GFG { 
  
    // Driver code 
    public static void main(String[] args) 
    { 
  
        // Creating a Stream of Strings 
        Stream<String> stream = Stream.of("Geeks", "fOr", 
                                          "GEEKSQUIZ", "GeeksforGeeks"); 
  
        // Using Stream filter(Predicate predicate) 
        // to get a stream consisting of the 
        // elements having UpperCase Character 
        // at index 1 
        stream.filter(str -> Character.isUpperCase(str.charAt(1))) 
            .forEach(System.out::println); 
    } 
} 

Output :

fOr
GEEKSQUIZ

Example 3 : filter() method with operation of filtering out the elements ending with s.

// Java code for Stream filter 
// (Predicate predicate) to get a stream 
// consisting of the elements of this 
// stream that match the given predicate. 
import java.util.stream.Stream; 
  
class GFG { 
  
    // Driver code 
    public static void main(String[] args) 
    { 
  
        // Creating a Stream of Strings 
        Stream<String> stream = Stream.of("Geeks", "foR", 
                                          "GeEksQuiz", "GeeksforGeeks"); 
  
        // Using Stream filter(Predicate predicate) 
        // to get a stream consisting of the 
        // elements ending with s 
        stream.filter(str -> str.endsWith("s")) 
            .forEach(System.out::println); 
    } 
} 

Output :

Geeks
GeeksforGeeks

My Personal Notes

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