修改ArrayList里面的内容

public static void main(String [] as){ Student a = new Student("a", 80); Student b = new Student("b", 90); Student c = new Student("c", 70); List<Student> list = new ArrayList<Student>(); list.add(a); list.add(b); list.add(c); System.out.println("未修改前:"); for(Student s: list){ System.out.println(s); } a.setMark(100); list.set(0, a); System.out.println("已修改后:"); for(Student s: list){ System.out.println(s); }}}