優先佇列的申明：

 Queue<Student> queue = new PriorityQueue<>();

要使得優先佇列的排序起作用，就要讓這個student實現Comparable中的compareTo方法

 @Override
    public int compareTo(Object o) {
        Student another = (Student) o;
        Integer anotherAge = another.age;
        if (this.age < anotherAge) {
            
 
return -1;
        } else if (this.age == anotherAge) {
            return 0;
        }
        return 1;
    }

我在這裡是按年齡排序，年齡小的返回-1，也就是正常情況下，這樣優先佇列裡每次取出的就是年齡最小的那個student

此外關於重寫equals問題

例如

@Override
    public boolean equals(Object obj) {
        Student another = (Student) obj;
        if (another.name.equals(this
 
.name)) {
            return true;
        }
        return false;
    }

  Student student1 = new Student("1", 20, "徐康");
  Student student2 = new Student("2", 21, "徐康");

呼叫student1.equals(student2)返回true

Stack<Student> students=new Stack<>();
students.add(student1);
System.out.println(students.contains(student2));

List
 
<Student> list=new ArrayList<>();
list.add(student1);
System.out.println(list.contains(student2));

兩個都輸出true