准备一个实体类

public class Student {
    private String name;
    private int age;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }
}

准备一个List集合

        List<Student> list=new ArrayList<>();
        Student s1=new Student();
        s1.setName("张三");
        s1.setAge(18);
        list.add(s1);
        Student s2=new Student();
        s2.setName("李四");
        s2.setAge(22);
        list.add(s2);

传统的for循环

        //for循环
        for (int i=0;i< list.size();i++){
            System.out.println(list.get(i));
        }

        //增强for循环
        for(Student student: list){
            System.out.println(student);
        }
        //迭代器
        Iterator<Student> iterator = list.iterator();
        while (iterator.hasNext()){
            System.out.println(iterator.next());
        }

使用Stream流

        //遍历List集合
        list.stream().forEach(str->{
           System.out.println(str.getName()+":"+str.getAge());
        });
        //过滤 把名字为李四的过滤掉
        list.stream().filter(str -> !"李四".equals(str.getName())).forEach(str -> {
            System.out.println(str.getName()+":"+str.getAge());
        });
         //操作对象，拼接
       //String collect=list.stream().map(student->student.getName()).collect(Collectors.joining(",","前","后"));
       // System.out.println(collect);

先声明筛选条件，在遍历

 //声明一个条件 学生年龄大于18
 Predicate<Student> pred = (student) -> student.getAge() > 18;
 //调用方法
 selectStudent(list,pred);

 private static void selectStudent(List<Student> list, Predicate<Student> pred) {
        System.out.println("选出年龄大于18的学生：");
        list.forEach(student -> {
            if (pred.test(student)){
                System.out.println(student.getName()+":"+student.getAge());
            }
        });

    }

Stream操作嵌套循环（2层）

//java 8 stream操作 嵌套循环
        List<Student> list = list1.stream().filter(student1 -> list2.stream()
                .anyMatch(studnet2 -> student1.getName().equals(studnet2.getName()) ))
                .collect(Collectors.toList());
        System.out.println("stream操作筛选后的结果" + list.get(0).getName());