Object obj = new Object();
System.out.println(obj.hashCode()); //110718392
System.out.println(System.identityHashCode(obj)); //110718392
String str1 = "abc";
String str2 = new String("abc");
String str3 = "abc".intern();
System.out.println("hashCode:" + str1.hashCode() + " identityHashCode:" + System.identityHashCode(str1));
System.out.println("hashCode:" + str2.hashCode() + " identityHashCode:" + System.identityHashCode(str2));
System.out.println("hashCode:" + str3.hashCode() + " identityHashCode:" + System.identityHashCode(str3));
//hashCode:96354 identityHashCode:460141958
//hashCode:96354 identityHashCode:1163157884
//hashCode:96354 identityHashCode:460141958
System.out.println(str1 == str2); //false
System.out.println(str1 == str3); //true
总结：
在不重写hashCode的情况下，二者的值都是一样的。这三个字符串的hashCode都是相同的，这是因为String类重写hashCode方法，通过String的值生成hashCode值，所以只要值相同，hashCode就相同。str1与str2的identityHashCode不一样，是因为identityHashCode永远返回对象的内存地址，所以不相同；而str1与str3的identityHashCode相同，是因为intern方法会先从字符串常量池里获取字符串，所以二者的地址值相同。==比较的是两个对象的引用地址，所以str1 == str2返回false，(str1 == str3返回true。
