javastream流--基本操作与介绍(持续更新中,用到了我就更新!)

旧城等待， 2023-02-09 10:27 20阅读 0赞

### javastream在正常开发中使用到的地方还是蛮多了,在这里记一下基本方法的使用: ###

//学生类
    		private Integer id;
    	    private String sex;
    	    private Integer age;
    	    private Integer score;
    	
    	    public Student() { 
    	    }
    	
    	    public Student(Integer id, String sex, Integer age, Integer score) { 
    	        this.id = id;
    	        this.sex = sex;
    	        this.age = age;
    	        this.score = score;
    	    }
    	    //(get/set/toString方法自己写)
    		//学生数据
    		Student stuA = new Student(1, "A", 18, 184);
            Student stuB = new Student(2, "B", 19, 163);
            Student stuC = new Student(3, "C", 20, 175);
            Student stuD = new Student(4, "D", 21, 158);
            Student stuE = new Student(5, "E", 22, 170);
    
            ArrayList<Student> slist = new ArrayList<>();
    
            slist.add(stuA);
            slist.add(stuB);
            slist.add(stuC);
            slist.add(stuD);
            slist.add(stuE);

### 筛选信息(filter)\----->找出这些同学中20岁的同学打印学生信息 ###

//循环查找
    for (int i = 0; i < slist.size(); i++) { 
    	   if (slist.get(i).getAge() == 20){ 
    	            System.out.println(slist.get(i).toString());
    	        }
    	    }
    	    
    //stream流查找
    Stream<Student> studentStream = slist.stream()
                    .filter(student -> student.getAge() == 20);
    
    //输出数据:
    Student{ id=3, sex='C', age=20, score=175}

### 变成集合(collect)\----->从流数据变成集合数据 ###

List<Student> student1 = slist.stream()
                    .filter(student -> student.getAge() == 20)
                    .collect(Collectors.toList());
                    
    //输出数据:
    [Student{ id=3, sex='C', age=20, score=175}]