StringBuilder使用技巧

最近在在处理文件读写时需要对一个List对象中的每行记录进行字符串追加处理。但是在循环中每次new 一个新的StringBuilder开销太大，而StringBuilder又没有提供clear方法，怎么办，delete方法可以搞定。

BufferedWriter bufWriter = new BufferedWriter(
                           new FileWriter("d:\\test.txt"));
private static final String COMMA_SPLIT_SIGN = ",";
List
 addressList = new ArrayList

for(Address address : addressList){
    StringBuilder sb = new StringBuilder();
    sb.append(address.getProvince())
      .append(COMMA_SPLIT_SIGN )
      .append(address.getCity());
    bufWriter.write(sb.toString);
}

显然上面的这段代码在不停的new StringBuilder()，循环10000次，就new 10000个StringBuiler, 改动后如下

BufferedWriter bufWriter = new BufferedWriter(
                           new FileWriter("d:\\test.txt"));
private static final String COMMA_SPLIT_SIGN = ",";
List
 addressList = new ArrayList

StringBuilder sb = new StringBuilder();
for(Address address : addressList){
    sb.append(address.getProvince())
      .append(COMMA_SPLIT_SIGN )
      .append(address.getCity());
    bufWriter.write(sb.toString);
    sb.delete(0, sb.length);
}