各种比较，ObjectEquals

public class ObjectEquals {public static void main(String [] args){Person p1 = new Person(20);Person p2 = new Person(20);Person p3 = p1;Integer i1 = new Integer(11);Integer i2 = new Integer(11);//实际上下面是上面的缩写！！！Integer i3 = 25;Integer i4 = 25;//注意以下三行，当自动封装包用 ==比较时，比较的时候是Int比较，不能在前后加字符串，只有第三、四行是对的System.out.println("Integer i3 = new Integer(14) i3 == i4 :" + (i3 == i4) + " **false*把对比的整数放在字符串中间*因为不是指向同一个地址空间**");System.out.println("************ :" + i3 == i4 + " **false**因为不是指向同一个地址空间**");System.out.println(i3 == i4);System.out.println("i3.equals(i4) :" + i1.equals(i4) + " **true**比较内容**");Integer x = 129;//jdk1.5以后，自动装箱，如果装箱的是一个字节，那么该数据会被共享不会重新开辟空间。Integer y = 129;System.out.println(x==y);//System.out.println(x.equals(y));//trueCat c1 = new Cat(20);Cat c2 = new Cat(20);Cat c3 = new Cat(20);String a = "name" ;//int b = 1; for(int i = 0; i < 10; i++){a += i;}System.out.println("a: " + a);System.out.println("Integer i1 = new Integer(11) i1 == i2 :" + (i1 == i2) + " **false**因为不是指向同一个地址空间**");System.out.println("i1.equals(i2) :" + i1.equals(i2) + " **true**比较内容**");System.out.println("p1 == p2 :" + (p1 == p2) + " **false**因为不是指向同一个地址空间**");System.out.println("p1.equals(p2) :" + p1.equals(p2) + " **false**非基本数据类型对象包装类，先比较空间再比较内容**");System.out.println("p1 == p3 :" + (p1 == p3) + " **true**因为指向同一个地址空间**");System.out.println("p1.equals(p3) :" + p1.equals(p3) + " **true**因为指向同一个地址空间**");System.out.println("p1.eq(p2) :" + p1.eq(p2) + " **true**重写了比较对象里边的值的方法***");System.out.println("p1.equals(c1) :" + p1.equals(c1));//类型错误//System.out.println("p1.equals(c1) :" + p1.eq(c1));System.out.println("p1.hashCode() :" + p1.hashCode());System.out.println("p2.hashCode() :" + p2.hashCode());System.out.println("p3.hashCode() :" + p3.hashCode());System.out.println("Integer.toHexString(p1.hashCode()) :" + Integer.toHexString(p1.hashCode()));System.out.println("Integer.toHexString(p2.hashCode()) :" + Integer.toHexString(p1.hashCode()));System.out.println("Integer.toHexString(p3.hashCode()) :" + Integer.toHexString(p1.hashCode()));System.out.println("11 :" + Integer.toHexString(p1.hashCode()) == Integer.toHexString(p2.hashCode()));System.out.println("Integer.toHexString(p1.hashCode()) == Integer.toHexString(p3.hashCode()) :" + Integer.toHexString(p1.hashCode()) == Integer.toHexString(p3.hashCode()));System.out.println("p1.getAge() == c1.getAge():" + ( p1.getAge() == c1.getAge() ));System.out.println("p1.toString() :" +p1.toString());System.out.println("p2.toString() :" +p2.toString());System.out.println("p3.toString() :" +p3.toString());System.out.println("p1.getClass().getName() $ Integer.toHexString(p1.hashCode()) :" + p1.getClass().getName()+"$"+Integer.toHexString(p1.hashCode()));}}class Person{private int age;public int getAge() {return age;}public void setAge(int age) {this.age = age;}public Person(int age) {this.age = age;}public boolean eq(Object obj){if(! (obj instanceof Person) ){throw new ClassCastException("类型错误"); }Person p = (Person)obj;return this.age == p.age;}}class Cat{private int age;public int getAge() {return age;}public void setAge(int age) {this.age = age;}public Cat(int age) {this.age = age;}}