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Java ????

?????

??????????????????????????????

• ?????????????
• ??????????????
• ???????????????

???Java????????????????????????????????

???????

??????????????????

• ?????boolean add(Object obj)
  ???????????
• ???????boolean addAll(Collection c)
  ???????????????????
• ?????void clear()
  ??????????
• ???????boolean contains(Object o)
  ?????????????
• ?????boolean equals(Object o)
  ??????????????
• ????boolean isEmpty()
  ????????
• ?????boolean remove(Object o)
  ??????????
• ???????int size()
  ??????????
• ??????Object[] toArray()
  ????????

Java???????

???????

// ????
Collection collection = new ArrayList();
// ????
collection.add(new Student("??", 20));
collection.add(new Student("??", 21));
collection.add(new Student("??", 22));
// ??????
System.out.println("?????" + collection.size()); // ???3

???????

???????????????

// ????????
for (Object obj : collection) {
    Student stu = (Student) obj;
    System.out.println(stu.toString());
}

2. ????

// ?????
Iterator it = collection.iterator();
// ????
while (it.hasNext()) {
    Student s = (Student) it.next();
    System.out.println(s.toString());
}

??????????

// ??????????
System.out.println(collection.contains(new Student("??", 21))); // ???true
System.out.println(collection.isEmpty()); // ???false

???????

// ??????
collection.remove(new Student("??", 21));
System.out.println("?????" + collection.size()); // ???1

??????????

?????????????????????????????????

???Student?

public class Student {
    private String name;
    private int age;
    public Student(String name, int age) {
        super();
        this.name = name;
        this.age = age;
    }
    public Student() {
    }
    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;
    }
    @Override
    public String toString() {
        return "Student [name=" + name + ", age=" + age + "]";
    }
    @Override
    public boolean equals(Object obj) {
        // ??????????
        if (this == obj) {
            return true;
        }
        // ????????
        if (obj == null) {
            return false;
        }
        // ??????
        if (obj instanceof Student) {
            Student s = (Student) obj;
            // ????
            return this.name.equals(s.getName()) && this.age == s.getAge();
        }
        return false;
    }
}

???????

public class Test {
    public static void main(String[] args) {
        // ????
        Collection collection = new ArrayList();
        // ??????
        Student s1 = new Student("??", 20);
        Student s2 = new Student("??", 21);
        Student s3 = new Student("??", 22);
        collection.add(s1);
        collection.add(s2);
        collection.add(s3);
        System.out.println("?????" + collection.size()); // ???3
        // ????????
        for (Object obj : collection) {
            Student stu = (Student) obj;
            System.out.println(stu.toString());
        }
        // ???????
        Iterator it = collection.iterator();
        while (it.hasNext()) {
            Student s = (Student) it.next();
            System.out.println(s.toString());
        }
        // ????????????
        System.out.println(collection.contains(s1)); // ???true
        System.out.println(collection.contains(new Student("??", 21))); // ???true
        // ????????
        System.out.println(collection.isEmpty()); // ???false
        // ????
        collection.remove(s1);
        System.out.println("?????" + collection.size()); // ???2
        collection.remove(new Student("??", 21));
        System.out.println("?????" + collection.size()); // ???1
    }
}