public boolean equals(Object obj) {
        return (this == obj);
    }

private final char value[];
public boolean equals(Object anObject) {
    if (this == anObject) {  //如果引用地址是否一致
        return true;
    }
    if (anObject instanceof String) {   //如果傳進來的是String類型
        String anotherString = (String)anObject;  //向下轉型
        int n = value.length;
        if (n == anotherString.value.length) {  //如果當前字符串長度和被傳入的字符串長度一致
            char v1[] = value;
            char v2[] = anotherString.value;
            int i = 0;
            while (n-- != 0) {  
                if (v1[i] != v2[i])  //如果兩者轉化成的字符數組中某個索引位置的值不一樣
                    return false;
                i++;
            }
            return true;
        }
    }
    return false;
}

public class User implements Serializable {
    private String name;
    private int age;
    //set,get方法

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;  //如果引用地址一樣
        if (o == null || getClass() != o.getClass()) return false;  //如果傳入的o是null或者傳入的o不是User類型

        User user = (User) o;  

        if (age != user.age) return false;  //一個個屬性分別比較是否一致
        return name.equals(user.name);
    }

}