java SringBuilder 字符串生成器

提高频繁增加字符串的效率

 

String str="";
long starttime=System.currentTimeMillis();
for(int i=0;i<10000;i++)
{
    str=str+i;
}
long endtime=System.currentTimeMillis();
long time1 =endtime-starttime;
System.out.println("time1:"+time1);
StringBuilder strbuilder=new StringBuilder("");
starttime=System.currentTimeMillis();
for(int i=0;i<10000;i++)
{
    strbuilder.append(i);
}
endtime=System.currentTimeMillis();
long time2 =endtime-starttime;
System.out.println("time2:"+time2);
/*输出结果：
time1:974
time2:1
*/

append(content)//content可以是任何类型的数据或者其他对象

insert(int offset,arg)// offset,该参数必须大于等于0，且小于等于此序列的长度

StringBuilder strb=new StringBuilder("Hello");
strb.insert(1, "&");
System.out.println(strb);//输出结果：H&ello

 

delete(int start,int end)//start,将要删除的字符串的起点；end,将要删除的字符串的终点

StringBuilder strb=new StringBuilder("Hello");
strb.delete(1,2);
System.out.println(strb);//输出结果：Hllo