stream api 中 list to map and to list

学习stream api 记录一下笔记

public class StreamToMap {
	List<Student> list = Arrays.asList(new Student(1, 18, "阿才"),
            new Student(2, 18, "小强" ),
            new Student(3, 18, "啊星"));
		@Test
		public void listToMap(){
			  / /jdk1.8 lambda 表达式
			 Map<Integer, Student> map = list.stream().collect(Collectors.toMap(Student::getId, student->student));
			  // 遍历打印结果
				map.forEach((key, value) -> {
				System.out.println("key: " + key + "    value: " + value);
			});
		}
		
		@Test
		public void listToMapByName){
			// value 为对象中的属性
			Map<Integer, String> map = list.stream().collect(Collectors.toMap(Student::getId, Student::getName));
			map.forEach((key, value) -> {
			System.out.println("key: " + key + "    value: " + value);
		});
       }
		
		@Test
		public void listToListByName(){
			// value 为对象中的属性
			List< String> list1 = list.stream().map(e -> e.getName()).collect(Collectors.toList());
			list1.forEach((value) -> {
			  System.out.println( "value: " + value);
		});
       }
		
		@Test
		public void listToList(){  
			List<String> wordList = new ArrayList<>();
			wordList.add("a");
			wordList.add("b");
			wordList.add("c");
			// value 为对象中的属性
			List<String> output = wordList.stream().
					map(String::toUpperCase).
					collect(Collectors.toList());		
			output.forEach((value)-> System.out.println(value));
       }
		
		@Test
		public void filtList() {
			Integer[] sixNums = {1, 2, 3, 4, 5, 6};
			Integer[] evens =
			Stream.of(sixNums).filter(n -> n%2 == 0).toArray(Integer[]::new);  //过滤操作
			System.out.println(evens[0]);
		}

}	
		
		
class Student{	
	Integer id;
	Integer age;
	String name;	
	public Student(Integer id, Integer age, String name) {
		super();
		this.id = id;
		this.age = age;
		this.name = name;
	}
		public Integer getId() {
			return id;
		}
		public void setId(Integer id) {
			this.id = id;
		}
		public Integer getAge() {
			return age;
		}
		public void setAge(Integer age) {
			this.age = age;
		}
		public String getName() {
			return name;
		}
		public void setName(String name) {
			this.name = name;
		}
		
	
}