Java 中字符串拼接 String 和 StringBuilder（StringBuffer）的使用

public static void main(String[] args) {
try {
int count = 500;

long begin = System.currentTimeMillis();
testString(count);
long end = System.currentTimeMillis();
long time = end - begin;
System.out.println("String 方法拼接"+count+"次消耗时间：" + time + "毫秒");

begin = System.currentTimeMillis();
testStringBuilder(count);
end = System.currentTimeMillis();
time = end - begin;
System.out.println("StringBuilder 方法拼接"+count+"次消耗时间：" + time + "毫秒");

} catch (Exception e) {
e.printStackTrace();
}

}

private static String testString(int count) {
String result = "";

for (int i = 0; i < count; i++) {
result += "hello ";
}

return result;
}

private static String testStringBuilder(int count) {
StringBuilder sb = new StringBuilder();

for (int i = 0; i < count; i++) {
sb.append("hello");
}

return sb.toString();
}

String 方法拼接500次消耗时间：2毫秒
StringBuilder 方法拼接500次消耗时间：0毫秒

String 方法拼接50000次消耗时间：4973毫秒
StringBuilder 方法拼接50000次消耗时间：3毫秒