排序写法+jdk8的lambada简单样例

最新推荐文章于 2024-01-30 21:59:26 发布

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本文通过多个示例介绍了如何在Java中使用JDK8的Stream API和Lambda表达式进行列表排序，包括传统Comparator接口实现、Lambda表达式简化及自然排序方法。

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为熟悉jdk8的stream，lambada写法，特编写一些简单示例如下：

先上一个排序，使用了lambda表达式的演变图：

代码如下：

public void test1() {
		System.out.println("##########test1##########");
		
		//jdk8以前的写法，Comparator接口实现的参数
		List<String> list01 = Arrays.asList("a","b","g","f","e","c","d");
		list01.sort(new Comparator<String>() {
			public int compare(String e1, String e2) {
				// TODO Auto-generated method stub
				return e1.compareTo(e2);
			}
		});
		System.out.println("=======list01======");
		System.out.println(JSON.toJSON(list01));
		
		//尝试使用lambada表达式
		List<String> list02 = Arrays.asList("a","b","g","f","e","c","d");
		list02.sort((String e1,String e2) -> {
			int a = e1.compareTo(e2);
			return  a ;
		});
		System.out.println("======list02=======");
		System.out.println(JSON.toJSON(list02));
		
		//lambada表达式简化版本
		List<String> list03 = Arrays.asList("a","b","g","f","e","c","d");
		list03.sort((e1,e2) ->  e1.compareTo(e2));
		System.out.println("=======list03======");
		System.out.println(JSON.toJSON(list03));
		
		//lambada表达式进一步简化
		List<String> list04 = Arrays.asList("a","b","g","f","e","c","d");
		list04.sort(String::compareTo);
		System.out.println("=====list04========");
		System.out.println(JSON.toJSON(list04));
		System.out.println();
		
		
	}

其他方式实现排序：

public void test2() {
		
		System.out.println("##########test2##########");
		
		//使用Collections类的sort方法
		List<String> list05 = Arrays.asList("a","b","g","f","e","c","d");
		Collections.sort(list05,(e1,e2) ->  e1.compareTo(e2));
		System.out.println("=====list05========");
		System.out.println(JSON.toJSON(list05));
		
		//使用stream的sort方法2
		List<String> list06 = Arrays.asList("a","b","g","f","e","c","d");
		List<String> list07 = list06.stream()
				.sorted((e1,e2) -> e1.compareTo(e2))
				.collect(Collectors.toList());
		System.out.println("=======list07======");
		System.out.println(JSON.toJSON(list07));
		
		//使用Comparator接口的naturalOrder方法
		List<String> list08 = Arrays.asList("a","b","g","f","e","c","d");
		list08.sort(Comparator.naturalOrder());
		System.out.println("======list08=======");
		System.out.println(JSON.toJSON(list08));
	}

测试方法：

public static void main(String[] args) {
		
		List<String> list00 = Arrays.asList("a","b","g","f","e","c","d");
		List<String> list = list00.stream().sorted().collect(Collectors.toList());
		System.out.println(JSON.toJSON(list));
		
		new TestCompareStream().test1();
		new TestCompareStream().test2();
	}

执行结果：如图：最终的排序结果都一样。