判断下面的代码
class Person{
private String name;
private int age;
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;
}
public Person(String name, int age) {
super();
this.name = name;
this.age = age;
}
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + age;
result = prime * result + ((name == null) ? 0 : name.hashCode());
return result;
}
@Override
public boolean equals(Object obj) {
if (this == obj)
return true;
if (obj == null)
return false;
if (getClass() != obj.getClass())
return false;
Person other = (Person) obj;
if (age != other.age)
return false;
if (name == null) {
if (other.name != null)
return false;
} else if (!name.equals(other.name))
return false;
return true;
}
}
public class TestString {
public static void main(String[] args) {
Person p1 = new Person("AA", 12);
Person p2 = new Person("AA", 12);
System.out.println(p1 == p2);//1
System.out.println(p1.equals(p2));//2
//关于String
String str1 = "AA";
String str2 = "AA";
String str3 = new String("AA");
System.out.println(str1 == str2);//3
System.out.println(str1.equals(str2));//4
System.out.println(str1 == str3);//5
System.out.println(str1.equals(str3));//6
System.out.println(p1.getName() == p2.getName());//7
}
}
运行结果与分析:
false:通过new创建的对象都是放在堆中,二者的引用地址不同
true:自定义类型的equals()方法,要重写以后才是比较的内容
true:str1和str2共同指向字符串常量池中的一块内存
true:str1和str2内容一样,指向地址也一样,这个true是必然的
false:str3是一个引用对象,其实内部实现还是指向的同一个字符串,但这里是那引用地址来比,故为false
true:str3的内容确实是和Str1相同,且最终是同一个"AA"常量
true:再次说明了P1和P2的name属性指向的地址其实还是字符串常量池中的"AA"
画图说明: