String和StringBuffer的区别，和大多数讲区别的不一样

String str1="hhhh";
String str2=str1;
str2+="aaaa";
StringBuffer str3=new StringBuffer("qqqq");
StringBuffer str4=str3;
str4.append("bbbb");
System.out.println(str1.toString());
System.out.println(str2.toString());
System.out.println(str1.hashCode());
System.out.println(str2.hashCode());
System.out.println(str3.toString());
System.out.println(str4.toString());
System.out.println(str3.hashCode());

System.out.println(str4.hashCode());

执行：

hhhh
hhhhaaaa
3201536
1751214656
qqqqbbbb
qqqqbbbb
366712642

366712642

自己体会