我測試下面的sting.split。字符串分割後的性能下降一個代碼
import java.io.File;
public class TestSplit3 {
private static final String PROCFS = "/proc/";
public static void main(String[] args) {
//split();
testfile(Integer.parseInt(args[0]) > 0);
split();
}
private static void testfile(Boolean flag) {
long start = System.currentTimeMillis();
if (flag) {
for (int i = 0; i < 1000; i++) {
new File(PROCFS + i);
}
}
System.out.println("newfile:" + (System.currentTimeMillis() - start));
}
public static void split() {
long start = System.currentTimeMillis();
for (int j = 0; j < 1000; j++) {
for (int i = 0; i < 1000; i++) {
String str = "asas asa s asas asas asa sa sas as as as a a"
+ "asa sasa sa sa sas as as asas as as as as as as"
+ "as as a sas asdasdas dasd asda sd ada d";
str.toString().split(" ");
}
}
System.out.println("split:" + (System.currentTimeMillis() - start));
}
}
and test result: [[email protected] longer]$ ~/opt/taobao/install/jdk-1.7.0_10/bin/java TestSplit3 0 newfile:0 split:1772 [[email protected] longer]$ ~/opt/taobao/install/jdk-1.7.0_10/bin/java TestSplit3 1 newfile:6 split:1763 [[email protected] longer]$ ~/jdk-1.6.0_32/bin/java TestSplit3 0 newfile:0 split:2833 [[email protected] longer]$ [[email protected] longer]$ ~/jdk-1.6.0_32/bin/java TestSplit3 1 newfile:5 split:3416
E,在JDK7,運行時間是一致的。但在JDK6, 'TestSplit3 0' 比 'TestSplit3 1' 更快。 誰能告訴我爲什麼??以及如何改進jdk6
是不是3416ms超過2833ms慢? – johnchen902 2013-04-20 06:29:07
是的。 3416ms比2833ms慢。因爲testfile.i很困惑 – fengshen 2013-04-20 06:31:15
你說'TestSplit3 1'比'TestSplit3 0'更快 – johnchen902 2013-04-20 06:32:23