Java 8 forEach打印带有索引

ゞ浴缸里的玫瑰 2023-02-15 05:14 80阅读 0赞

一个简单的Java 8技巧可以在前面打印带有索引的`Array`或`List` 。

## 1.带索引的数组 ##

使用`IntStream.range`生成索引。

JavaListWithIndex.java

package com.mkyong.java8;
    
    import java.util.List;
    import java.util.stream.Collectors;
    import java.util.stream.IntStream;
    
    public class JavaArrayWithIndex {
    
        public static void main(String[] args) {
    
            String[] names = {"Java", "Node", "JavaScript", "Rust", "Go"};
    
            List<String> collect = IntStream.range(0, names.length)
                    .mapToObj(index -> index + ":" + names[index])
                    .collect(Collectors.toList());
    
            collect.forEach(System.out::println);
    
        }
    
    }

输出量

0:Java
    1:Node
    2:JavaScript
    3:Rust
    4:Go

## 2.索引清单 ##

将`List`转换为`Map` ，并使用`Map.size`作为索引。

Stream.java

<R> R collect(Supplier<R> supplier,
                      BiConsumer<R, ? super T> accumulator,
                      BiConsumer<R, R> combiner);

JavaListWithIndex.java

package com.mkyong.java8;
    
    import java.util.Arrays;
    import java.util.HashMap;
    import java.util.List;
    
    public class JavaListWithIndex {
    
        public static void main(String[] args) {
    
            List<String> list = Arrays.asList("Java", "Node", "JavaScript", "Rust", "Go");
    
            HashMap<Integer, String> collect = list
                    .stream()
                    .collect(HashMap<Integer, String>::new,
                            (map, streamValue) -> map.put(map.size(), streamValue),
                            (map, map2) -> {
                            });
    
            collect.forEach((k, v) -> System.out.println(k + ":" + v));
    
        }
    
    }

输出量

0:Java
    1:Node
    2:JavaScript
    3:Rust
    4:Go

## 参考文献 ##

*  [Stream.collect JavaDoc][]
 *  Java 8 BiConsumer示例
 *  Java 8 forEach示例

标签： [消费者][Link 1] [foreach][] [intstream][] [Java 8][] [循环][Link 2] [映射][Link 3]

> 翻译自: [https://mkyong.com/java8/java-8-foreach-print-with-index/][https_mkyong.com_java8_java-8-foreach-print-with-index]

[Stream.collect JavaDoc]: https://docs.oracle.com/javase/8/docs/api/java/util/stream/Stream.html#collect-java.util.function.Supplier-java.util.function.BiConsumer-java.util.function.BiConsumer-
[Link 1]: https://mkyong.com/tag/consumer/
[foreach]: https://mkyong.com/tag/foreach/
[intstream]: https://mkyong.com/tag/intstream/
[Java 8]: https://mkyong.com/tag/java-8/
[Link 2]: https://mkyong.com/tag/loop/
[Link 3]: https://mkyong.com/tag/map/
[https_mkyong.com_java8_java-8-foreach-print-with-index]: https://mkyong.com/java8/java-8-foreach-print-with-index/