-两个对象值相同(xequals(y) == true)但却可有不同的hash code这句话应该是对的吧

答：对的，相等性比较和hashCode的计算依据可以由类的编写者确定

（此题的答案，各个论坛上五花八门，我做了以下三个测试，说明很多问题）

一：//hashCode相同 .equals返回false

public class TestEqual {

public static void main(String[] args) {

Person per1 = new Person(3);

Person per2 = new Person(4);

System.out.println(per1.equals(per2));

//hashCode相同 per1.equals(per2)返回false

}

}

class Person{

public int age;

public Person(int age) {

this.age = age;

}

public Person() {

}

public boolean equals(Object arg0) {

return false;

}

@Override

public int hashCode() {

return 4;

}

}

//以上返回false

二：//hashCode值是不同的，equals返回true

public class TestEqual {

public static void main(String[] args) {

Person per1 = new Person(3);

Person per2 = new Person(4);

System.out.println(per1.equals(per2));

//hashCode值是不同的，per1.equals(per2)返回true

}

}

class Person{

public int age;

public Person(int age) {

this.age = age;

}

public Person() {

}

public boolean equals(Object arg0) {

return true;

}

@Override

public int hashCode() {

Random ran = new Random();

return ran.nextInt();

}

}

//以上返回true

三：//相同的对象，equals返回false。

public class TestEqual {

public static void main(String[] args) {

Person per1 = new Person(3);

Person per2 = per1;

System.out.println(per1.equals(per2));//false

System.out.println(per1.equals(per1));//false

System.out.println(per1==per2);//true

//相同的对象，per1.equals(per2)返回false。

}

}

class Person{

public int age;

public Person(int age) {

this.age = age;

}

public Person() {

}

public boolean equals(Object arg0) {

return false;

}

public int hashCode() {

Random ran = new Random();

return ran.nextInt();

}

}