应一个大量字符串拼接的任务
测试一下StringBuilder、StringBuffer、String在操作字符串拼接时候的性能
性能上理论是StringBuilder > StringBuffer > String
测试方法：
创建一个StirngTest类含有静态常量字符串是26个字母，以及一个循环轮数
在测试时采用循环来操作字符串的拼接，计算操作时间并输出：
package com.test.xlc;
import java.util.Random;
public class StringTest {
static final String strFinal = "abcdefghijklmnopqrstovwxyz";
static final int forInt = 100;
static void StringBuilderTest() {
Random rand = new Random(47);
StringBuilder strB = new StringBuilder();
long start = System.currentTimeMillis();
for(int i = 0; i < forInt; ++i) {
int randInt = rand.nextInt(23);
strB.append(strFinal.substring(randInt, randInt + 4));
}
long end = System.currentTimeMillis();
// System.out.println(strB.toString());
System.out.println("StringBuilderTest:" + (end - start));
}
static void StringBufferTest() {
Random rand = new Random(47);
StringBuffer strB = new StringBuffer();
long start = System.currentTimeMillis();
for(int i = 0; i < forInt; ++i) {
int randInt = rand.nextInt(23);
strB.append(strFinal.substring(randInt, randInt + 4));
}
long end = System.currentTimeMillis();
// System.out.println(strB.toString());
System.out.println("StringBufferTest:" + (end - start));
}
static void StringOnly() {
Random rand = new Random(47);
String str = "";
long start = System.currentTimeMillis();
for(int i = 0; i < forInt; ++i) {
int randInt = rand.nextInt(23);
str += strFinal.substring(randInt, randInt + 4);
}
long end = System.currentTimeMillis();
// System.out.println(str);
System.out.println("String:" + (end - start));
}
public static void main(String...args) {
StringBuilderTest();
StringBufferTest();
StringOnly();
}
}
测试循环次数：
100
StringBuilderTest:0
StringBufferTest:0
String:0
1000
StringBuilderTest:1
StringBufferTest:0
String:7
10000
StringBuilderTest:2
StringBufferTest:2
String:217
100000
StringBuilderTest:12
StringBufferTest:10
String:17136
1000000
StringBuilderTest:55
StringBufferTest:53
我提前终止了
之后我又测试了拼接长串，本实验结果显示在拼接字符串的效率上：
StringBuffer > StringBuilder > String