StringBuilder與StringBuffer知多少

今天既然有人把StringBuilder與StringBuffer搞反了，在這裏抽點時間寫了個簡單測試給其參考：

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;


/**
 * 
 * @author ky
 *
 */
public class StringBuilderTester {
private static final String base = " base string. ";
private static final int count = 5000000;




public static void stringTest() {
 long begin, end;
 begin = System.currentTimeMillis();
 String test = new String(base);
 for (int i = 0; i < count/100; i++) {
  test = test + " add ";
 }
 end = System.currentTimeMillis();
 System.out.println((end - begin)
   + " millis has elapsed when used String. ");
}




public static void stringBufferTest() {
 long begin, end;
 begin = System.currentTimeMillis();
 StringBuffer test = new StringBuffer(base);
 for (int i = 0; i < count; i++) {
  test = test.append(" add ");
 }
 end = System.currentTimeMillis();
 System.out.println((end - begin)
   + " millis has elapsed when used StringBuffer. ");
}




public static void stringBuilderTest() {
 long begin, end;
 begin = System.currentTimeMillis();
 StringBuilder test = new StringBuilder(base);
 for (int i = 0; i < count; i++) {
  test = test.append(" add ");
 }
 end = System.currentTimeMillis();
 System.out.println((end - begin)
   + " millis has elapsed when used StringBuilder. ");
}




public static String appendItemsToStringBuiler(List list) {
 StringBuilder b = new StringBuilder();




 for (Iterator i = list.iterator(); i.hasNext();) {
  b.append(i.next()).append(" ");
 }




 return b.toString();
}




public static void addToStringBuilder() {
 List list = new ArrayList();
 list.add(" I ");
 list.add(" play ");
 list.add(" Bourgeois ");
 list.add(" guitars ");
 list.add(" and ");
 list.add(" Huber ");
 list.add(" banjos ");




 System.out.println(StringBuilderTester.appendItemsToStirngBuffer(list));
}




public static String appendItemsToStirngBuffer(List list) {
 StringBuffer b = new StringBuffer();




 for (Iterator i = list.iterator(); i.hasNext();) {
  b.append(i.next()).append(" ");
 }




 return b.toString();
}




public static void addToStringBuffer() {
 List list = new ArrayList();
 list.add(" I ");
 list.add(" play ");
 list.add(" Bourgeois ");
 list.add(" guitars ");
 list.add(" and ");
 list.add(" Huber ");
 list.add(" banjos ");




 System.out.println(StringBuilderTester.appendItemsToStirngBuffer(list));
}




public static void main(String[] args) {
 stringTest();
 stringBufferTest();
 stringBuilderTest();
 addToStringBuffer();
 addToStringBuilder();
}
}