判斷下面的代碼
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
//關於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
}
}
運行結果與分析:
false:通過new創建的對象都是放在堆中,二者的引用地址不同
true:自定義類型的equals()方法,要重寫以後纔是比較的內容
true:str1和str2共同指向字符串常量池中的一塊內存
true:str1和str2內容一樣,指向地址也一樣,這個true是必然的
false:str3是一個引用對象,其實內部實現還是指向的同一個字符串,但這裏是那引用地址來比,故爲false
true:str3的內容確實是和Str1相同,且最終是同一個"AA"常量
true:再次說明了P1和P2的name屬性指向的地址其實還是字符串常量池中的"AA"
畫圖說明: