javastream流--基本操作與介紹(持續更新中,用到了我就更新!)

javastream在正常開發中使用到的地方還是蠻多了,在這裏記一下基本方法的使用:

		//學生類
		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方法自己寫)
		//學生數據
		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);

篩選信息(filter)----->找出這些同學中20歲的同學打印學生信息

//循環查找
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);

//輸出數據:
Student{id=3, sex='C', age=20, score=175}

變成集合(collect)----->從流數據變成集合數據

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