測試代碼：

public class StringJoinTest { public static void main(String[] args) { int count = 10000; long begin, end, time; begin = System.currentTimeMillis(); testString(count); end = System.currentTimeMillis(); time = end - begin; System.out.println('拼接' + count + '次，String消耗時(shí)間：' + time + '毫秒'); begin = System.currentTimeMillis(); testStringBuffer(count); end = System.currentTimeMillis(); time = end - begin; System.out.println('拼接' + count + '次，StringBuffer消耗時(shí)間：' + time + '毫秒'); begin = System.currentTimeMillis(); testStringBuilder(count); end = System.currentTimeMillis(); time = end - begin; System.out.println('拼接' + count + '次，StringBuilder消耗時(shí)間：' + time + '毫秒'); } private static String testStringBuilder(int count) { StringBuilder tem = new StringBuilder(); for (int i = 0; i < count; i++) { tem.append('hello world!'); } return tem.toString(); } private static String testStringBuffer(int count) { StringBuffer tem = new StringBuffer(); for (int i = 0; i < count; i++) { tem.append('hello world!'); } return tem.toString(); } private static String testString(int count) { String tem = ''; for (int i = 0; i < count; i++) { tem += 'hello world!'; } return tem; }}

測試結(jié)果：

結(jié)論：

在少量字符串拼接時(shí)還看不出差別，但隨著數(shù)量的增加，String+拼接效率顯著降低。在達(dá)到100萬次，我本機(jī)電腦已經(jīng)無法執(zhí)行String+拼接了，StringBuilder效率略高于StringBuffer。所以在開發(fā)過程中通常情況下推薦使用StringBuilder。

StringBuffer和StringBuilder的區(qū)別在于StringBuffer是線程安全的。

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