Question

所以看起来我的java程序无法识别两个相同的对象，即使我使用的方法与之前的问题相同，其中java确实将两个对象识别为相同。这个程序的唯一区别是我有一个额外的keyboard.nextLine（），这是输入对象2的名称/地址所必需的。

这是课堂输入

    public boolean equals(Person num1) {
    if ((this.name==num1.name)&&(this.address==num1.address)&&
    (this.age==num1.age)&&(this.phoneNumber==num1.phoneNumber))
        return true;
    else
        return false;
}

这是演示输入

   import java.util.Scanner;
   public class PersonDemo {

   public static void main(String[] args) {

    Person num1, num2;
    num1=new Person();
    num2=new Person();

    String name, address;
    int age; 
    long phoneNumber;

    Scanner keyboard = new Scanner(System.in);

    System.out.println("Input the name of person 1:");
    name=keyboard.nextLine();
    System.out.println("Input the address of person 1:");
    address=keyboard.nextLine();
    System.out.println("Input the age of person 1:");
    age=keyboard.nextInt();
    System.out.println("Input the phone number of person 1:");
    phoneNumber=keyboard.nextLong();
    keyboard.nextLine();

    num1.setName(name);
    num1.setAddress(address);
    num1.setAge(age);
    num1.setPhoneNumber(phoneNumber);

    System.out.println("\nInformation of person 1: ");
    System.out.println(num1);

    System.out.println("\nInput the name of person 2:");
    name=keyboard.nextLine();
    System.out.println("Input the address of person 2:");
    address=keyboard.nextLine();
    System.out.println("Input the age of person 2:");
    age=keyboard.nextInt();
    System.out.println("Input the phone number of person 2:");
    phoneNumber=keyboard.nextLong();

    num2.setName(name);
    num2.setAddress(address);
    num2.setAge(age);
    num2.setPhoneNumber(phoneNumber);

    System.out.println("\nInformation of person 2: ");
    System.out.println(num2);

    if (num1.equals(num2))
        System.out.println("\nPerson 1 and person 2 are identical.");
    else 
        System.out.println("\nPerson 1 and person 2 are not identical.");
}


   }

Answer 1

对于Object(such as String)，您需要使用equals方法。 ==仅测试这两个对象是否是相同的对象（比较内存地址）。在您的情况下，num1.name和num2.name是不同的对象，尽管它们的内容是相同的。

Answer 2

问题：

没有正确覆盖Object.equals方法
在equals方法中，使用==而不是equals
没有测试num1 for null

这样做：

@Overrides
public boolean equals(Object num1) {
    boolean result = false;
    if (num1 != null && num1 instanceof Person) {
        Person personNum1 = (Person)num1;
        result = this.name.equals(personNum1.name) &&
                 this.address.equals(personNum1.address) &&
                 this.age.equals(personNum1.age) && 
                 this.phoneNumber.equals(personNum1.phoneNumber);
    }
    return result;
}

顺便说一句，关于equals的任何合理教程都会显示出这一点。：）

Java对象的识别相同

2 个答案: