String和StringBuffer互转

String转StringBuffer

1. 构造方法：StringBuffer sb = new StringBuffer(String);

String s  = "hello";
StringBuffer sb = new StringBuffer(s);

2. append()方法：

String s = "hello";
StringBuffer sb =  new StringBuffer();
sb.append(s);

StringBuffer转String

1. 构造方法

StringBuffer sb = new StringBuffer();
String s  = new String(sb);

2. toString()方法

StringBuffer sb = new StringBuffer("hello");
String s = sb.toString();

3. substring(int start ,int end)方法

StringBuffer sb = new StringBuffer("hello");
String s = sb.substring(0,sb.length());