Lambda表达式3:Stream的映射

Dear 丶 2024-04-19 14:51 61阅读 0赞

### 1、基础介绍 ###

> map-接收Lambda，将元素转换成其他形态或提取信息。接收一个函数作为参数，该函数会被应用到每隔元素上，并将其映射成一个新的元素；

List<Student> list = Arrays.asList(
    			new Student(1,"张三",60),
    			new Student(2,"李四",70),
    			new Student(3,"王五",80),
    			new Student(4,"赵六",90),
    			new Student(4,"赵六",90),
    			new Student(4,"赵六",90),
    			new Student(5,"田七",100)); 
    @Test
    public void test1(){
    	List<String> list = Arrays.asList("aaa","bbb","ccc");
    	list.stream().map((str) -> str.toUpperCase())
    	.forEach(System.out::println);
    	
    	this.list.stream().map(Student::getName)
    	.forEach(System.out::println);
    }

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> flatMap-接收一个函数作为参数，将流中的每个值都换成另一个流，然后把所有流连接成一个流

@Test
    public void test2(){
    	List<String> list = Arrays.asList("aaa","bbb","ccc");
    	
    	Stream<Stream<Character>> stream = list.stream()
    			.map(Test1::filterchar);// {
       {a,a,a},{b,b,b},{c,c,c}}
    	// 由于流中包含流，所有得要双重循环
    	stream.forEach((sm) -> sm.forEach(System.out::println));
    
    	
    	Stream<Character> stream2 = list.stream()
    			.flatMap(Test1::filterchar);// {a,a,a,b,b,b,c,c,c}
    	stream2.forEach(System.out::println);
    }
    
    
    public static Stream<Character> filterchar(String str){
    	List<Character> list = new ArrayList<Character>();
    	for (Character ch : str.toCharArray()) {
    		list.add(ch);
    	}
    	return list.stream();
    }

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2x3MzA1OTkzODk3_size_16_color_FFFFFF_t_70 1]

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