文章目錄
- 1.單線程性能對比
- 2.多線程性能對比
- 3.非線程安全SimpleDateFormat
- 4.線程安全DateTimeFormatter
- 5.結論
1.單線程性能對比
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.text.SimpleDateFormat;
public class Test{
public static void main(String[] args) {
String time = "20171231235959";
int count = 1000000;
String formats = "yyyyMMddHHmmss";
long s = System.nanoTime();
for(int i = 0; i < count ; i ++ ) {
DateTimeFormatter dtf = DateTimeFormatter.ofPattern(formats);
LocalDateTime.parse(time, dtf);
}
System.out.println( "DateTimeFormatter:\t" + ( System.nanoTime() - s) );
try {
s = System.nanoTime();
for(int i = 0; i < count ; i ++ ) {
SimpleDateFormat sdf = new SimpleDateFormat(formats);
sdf.parse(time);
}
System.out.println( "SimpleDateFormat:\t" + ( System.nanoTime() - s) );
}catch (Exception e) {
e.printStackTrace();
}
}
}
結果
DateTimeFormatter: 1075056771
SimpleDateFormat: 1777736489
2.多線程性能對比
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.text.SimpleDateFormat;
public class Test{
public static void main(String[] args) throws Exception{
for(int i = 0; i < 1000; i ++ ) {
dateThreadTest();
}
}
public static void dateThreadTest() throws InterruptedException {
List<Long> simlist = new ArrayList<>();
int count = 2000;
CountDownLatch countDownLatch = new CountDownLatch(count);
String time = "20171231235959";
String formats = "yyyyMMddHHmmss";
//DateTimeFormatter
CountDownLatch countDownLatch_fmt = new CountDownLatch(count);
List<Long> fmtlist = new ArrayList<>();
DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern(formats);
Runnable fmtrun = () -> {
long s = System.nanoTime();
for( int i = 0; i < 500 ; i ++ ) {
try {
LocalDateTime.parse(time, dateTimeFormatter);
} catch (Exception e) {
e.printStackTrace();
}
}
long e = System.nanoTime() - s;
synchronized(fmtlist) {
fmtlist.add( e );
}
countDownLatch_fmt.countDown();
};
for(int i = 0; i < count ; i ++ ) {
new Thread(fmtrun).start();
}
countDownLatch_fmt.await();
long fmtsum = 0;
for(Long fmtl : fmtlist ) {
fmtsum += fmtl;
}
int fmtsize = fmtlist.size();
long fmtavg = fmtsum / fmtsize;
System.out.println("DateTimeFormatter:\t" + fmtavg+ "-size:" + fmtsize);
//SimpleDateFormat
Runnable simrun = () -> {
long s = System.nanoTime();
SimpleDateFormat simpleDateFormat = new SimpleDateFormat(formats);
for( int i = 0; i < 500 ; i ++ ) {
try {
simpleDateFormat.parse(time);
} catch (ParseException e) {
e.printStackTrace();
}
}
long e = System.nanoTime() - s;
synchronized (simlist) {
simlist.add( e );
}
countDownLatch.countDown();
};
for(int i = 0; i < count ; i ++ ) {
new Thread(simrun).start();
}
countDownLatch.await();
long simsum = 0;
int simsize = simlist.size();
for(Long siml : simlist) {
simsum += siml;
}
long simavg = simsum / simsize;
System.out.println("SimpleDateFormat:\t" + simavg + "-size:" + simsize);
}
}
結果片斷
DateTimeFormatter: 320070-size:2000
SimpleDateFormat: 1579198-size:2000
DateTimeFormatter: 1149074-size:2000
SimpleDateFormat: 5590201-size:2000
DateTimeFormatter: 388116-size:2000
SimpleDateFormat: 1444295-size:2000
DateTimeFormatter: 391754-size:2000
SimpleDateFormat: 2403905-size:2000
DateTimeFormatter: 579022-size:2000
SimpleDateFormat: 1405484-size:2000
DateTimeFormatter: 575568-size:2000
SimpleDateFormat: 1565345-size:2000
DateTimeFormatter: 683145-size:2000
SimpleDateFormat: 2243927-size:2000
DateTimeFormatter: 2521980-size:2000
SimpleDateFormat: 3564548-size:2000
DateTimeFormatter: 452000-size:2000
SimpleDateFormat: 4381109-size:2000
DateTimeFormatter: 329263-size:2000
SimpleDateFormat: 476896-size:2000
DateTimeFormatter: 337858-size:2000
SimpleDateFormat: 510113-size:2000
DateTimeFormatter: 945077-size:2000
SimpleDateFormat: 1093366-size:2000
DateTimeFormatter: 854730-size:2000
SimpleDateFormat: 649053-size:2000
DateTimeFormatter: 379670-size:2000
SimpleDateFormat: 4156187-size:2000
DateTimeFormatter: 1214384-size:2000
SimpleDateFormat: 2089635-size:2000
DateTimeFormatter: 1309359-size:2000
SimpleDateFormat: 1360002-size:2000
DateTimeFormatter: 403218-size:2000
SimpleDateFormat: 643400-size:2000
DateTimeFormatter: 656442-size:2000
SimpleDateFormat: 12865579-size:2000
DateTimeFormatter: 1357402-size:2000
SimpleDateFormat: 556662-size:2000
DateTimeFormatter: 327016-size:2000
SimpleDateFormat: 689728-size:2000
DateTimeFormatter: 371160-size:2000
SimpleDateFormat: 852151-size:2000
DateTimeFormatter: 1296601-size:2000
SimpleDateFormat: 3495863-size:2000
DateTimeFormatter: 1382038-size:2000
SimpleDateFormat: 557998-size:2000
DateTimeFormatter: 408569-size:2000
SimpleDateFormat: 2498495-size:2000
DateTimeFormatter: 1658727-size:2000
SimpleDateFormat: 768303-size:2000
DateTimeFormatter: 412967-size:2000
SimpleDateFormat: 476698-size:2000
DateTimeFormatter: 335527-size:2000
SimpleDateFormat: 469686-size:2000
DateTimeFormatter: 568296-size:2000
SimpleDateFormat: 559510-size:2000
DateTimeFormatter: 398402-size:2000
SimpleDateFormat: 468114-size:2000
DateTimeFormatter: 538794-size:2000
SimpleDateFormat: 523629-size:2000
DateTimeFormatter: 427579-size:2000
SimpleDateFormat: 2054706-size:2000
DateTimeFormatter: 424820-size:2000
SimpleDateFormat: 552673-size:2000
DateTimeFormatter: 418098-size:2000
SimpleDateFormat: 996775-size:2000
DateTimeFormatter: 323411-size:2000
SimpleDateFormat: 826378-size:2000
DateTimeFormatter: 329768-size:2000
SimpleDateFormat: 664224-size:2000
DateTimeFormatter: 334381-size:2000
SimpleDateFormat: 577824-size:2000
DateTimeFormatter: 670466-size:2000
SimpleDateFormat: 3654294-size:2000
DateTimeFormatter: 348893-size:2000
SimpleDateFormat: 1214426-size:2000
DateTimeFormatter: 961402-size:2000
SimpleDateFormat: 625569-size:2000
DateTimeFormatter: 318604-size:2000
SimpleDateFormat: 1610296-size:2000
DateTimeFormatter: 395029-size:2000
SimpleDateFormat: 1112620-size:2000
DateTimeFormatter: 317822-size:2000
SimpleDateFormat: 6746071-size:2000
3.非線程安全SimpleDateFormat
import java.text.SimpleDateFormat;
public class Test{
public static void main(String[] args) {
SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyyMMddHHmmss");
String[] dates = {"20180101120000","20180912010000","20181101210000"};
Runnable runnable = () -> {
for(int i =0; i < 500; i ++ ) {
String string = dates[i % 3];
try {
if( string.length() > 0 ) {
Date date = simpleDateFormat.parse(string);
String stringnew = simpleDateFormat.format(date);
//對同一時間字串進行parse和fromat後比較是否一樣
boolean issame = string.equals(stringnew);
if( !issame ) {//前後不一樣，進行輸出
System.out.println(issame + "-" + string + "-" + stringnew);
break;
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
};
for(int i = 0; i < 10000; i ++ ) {
new Thread(runnable).start();
}
}
}
SimpleDateFormat多線程-結果片斷
false-20181101210000-00211101210000
at com.cgs.hb.TestMain.lambda$0(TestMain.java:56)
at java.lang.Thread.run(Thread.java:748)
java.lang.NumberFormatException: For input string: "1."
at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
at java.lang.Long.parseLong(Long.java:589)
at java.lang.Long.parseLong(Long.java:631)
at java.text.DigitList.getLong(DigitList.java:195)
at java.text.DecimalFormat.parse(DecimalFormat.java:2084)
at java.text.SimpleDateFormat.subParse(SimpleDateFormat.java:1867)
at java.text.SimpleDateFormat.parse(SimpleDateFormat.java:1514)
at java.text.DateFormat.parse(DateFormat.java:364)
at com.cgs.hb.TestMain.lambda$0(TestMain.java:56)
at java.lang.Thread.run(Thread.java:748)
java.lang.NumberFormatException: multiple points
at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:1890)
at sun.misc.FloatingDecimal.parseDouble(FloatingDecimal.java:110)
at java.lang.Double.parseDouble(Double.java:538)
at java.text.DigitList.getDouble(DigitList.java:169)
at java.text.DecimalFormat.parse(DecimalFormat.java:2089)
at java.text.SimpleDateFormat.subParse(SimpleDateFormat.java:2160)
at java.text.SimpleDateFormat.parse(SimpleDateFormat.java:1514)
at java.text.DateFormat.parse(DateFormat.java:364)
at com.cgs.hb.TestMain.lambda$0(TestMain.java:56)
at java.lang.Thread.run(Thread.java:748)
java.lang.NumberFormatException: For input string: ""
at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
at java.lang.Long.parseLong(Long.java:601)
at java.lang.Long.parseLong(Long.java:631)
at java.text.DigitList.getLong(DigitList.java:195)
at java.text.DecimalFormat.parse(DecimalFormat.java:2084)
at java.text.SimpleDateFormat.subParse(SimpleDateFormat.java:2160)
at java.text.SimpleDateFormat.parse(SimpleDateFormat.java:1514)
at java.text.DateFormat.parse(DateFormat.java:364)
at com.cgs.hb.TestMain.lambda$0(TestMain.java:56)
at java.lang.Thread.run(Thread.java:748)
false-20180101120000-20181101210000
4.線程安全DateTimeFormatter
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
public class Test{
public static void main(String[] args) {
DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern("yyyyMMddHHmmss");
String[] dates = {"20180101120000","20180912010000","20181101210000"};
Runnable runnable = () -> {
for(int i =0; i < 500; i ++ ) {
String string = dates[i % 3];
try {
if( string.length() > 0 ) {
LocalDateTime date = LocalDateTime.parse(string, dateTimeFormatter);
String stringnew = date.format(dateTimeFormatter);
//對同一時間字串進行parse和fromat後比較是否一樣
boolean issame = string.equals(stringnew);
if( !issame ) {//前後不一樣，進行輸出
System.out.println(issame + "-" + string + "-" + stringnew);
break;
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
};
for(int i = 0; i < 10000; i ++ ) {
new Thread(runnable).start();
}
}
}
DateTimeFormatter多線程-結果片斷
無輸出
5.結論
1.DateTimeFormatter線程安全，SimpleDateFormat非線程安全
2.單線程環境下DateTimeFormatter+LocalDateTime的parse性能比SimpleDateFormat的parse性能高
3.多線程環境下DateTimeFormatter作為共享變量時，大部分情況下性能比SimpleDateFormat高(因為多線程環境的複雜性，此結論不一定準确)
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