Java Stream filter()用法及代码示例

流过滤器(谓词谓词)返回一个由与此给定谓词匹配的流元素组成的流。这是一个中间操作。这些操作总是很懒惰，即执行诸如filter()之类的中间操作实际上并不执行任何过滤，而是创建一个新的流，该新流在遍历时将包含与给定谓词匹配的初始流的元素。

用法:

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.

示例1:filter()方法，用于滤除可被5整除的元素。

// 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); 
    } 
}

输出：

示例2:filter()方法，用于过滤索引为1的具有upperCase字母的元素。

// 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); 
    } 
}

输出：

fOr
GEEKSQUIZ

示例3:filter()方法，用于过滤出以s结尾的元素。

// 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); 
    } 
}

输出：

Geeks
GeeksforGeeks

相关用法

注：本文由纯净天空筛选整理自Sahil_Bansall大神的英文原创作品 Stream filter() in Java with examples。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。