Usage of String and StringBuilder

Usage
of String : String in java is read-only and there is no way to transform it, so StringBuilder needs to be used.

String.length() //获取字符串的长度
String.charAt(i) //获取第i个字符的内容
String.subString(start)   //获取[start,）的字符串
String.subString(start,end) //获取[start,end）中的字符串
char[] c = iniString.toCharArray() //将字符串转为char数组来进行改变字符内容
String.equal() //判断两个字符串是否相等

Usage of StringBuilder:
In addition to the methods supported in String, StringBuilder supports addition, deletion, and modification of characters.

stringBuilder.append("we");  //添加we在词尾
stringBuilder.insert(0,"we");//在0的位置加入后面的内容
stringBuilder.delete(0,1);  //删除[0,1)的数据
stringBuilder.deleteCharAt(0);
stringBuilder.setCharAt(0,'p'); //在某一个独特位置设置字符
char c = stringBuilder.charAt(i);//查询某个位置上的字符
System.out.println(stringBuilder);
new String(stringBuilder);//用stringBuilder来初始化String