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我是新來的併發Api，我只是製作程序並用線性和併發方式測試它。當我看到結果時，兩個結果都是一樣的，執行時間沒有差異。 代碼是如下： -使用並行與線性程序的結果沒有區別
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
public class TestFuture {
private static final ExecutorService threadpool = Executors.newFixedThreadPool(3);
public static void main(String[] a) throws InterruptedException, ExecutionException{
TestFuture testFuture=new TestFuture();
testFuture.testFutureTask();
Date start=new Date();
System.out.println("Start time :: "+start);
TestLinear testLinear=new TestLinear();
for (int i = 0; i < 3; i++) {
if(i==0){
testLinear.getFirstOutput();
System.out.println("time to done by every thread :: one "+new Date());
}else if(i==1){
testLinear.getSecondOutput();
System.out.println("time to done by every thread :: second "+new Date());
}else if(i==2){
testLinear.getThirdOutput();
System.out.println("time to done by every thread :: third "+new Date());
}
}
Date end=new Date();
System.out.println("End time :: "+end);
System.out.println("Difference :: "+((end.getTime()-start.getTime())/1000));
}
public void testFutureTask() throws InterruptedException, ExecutionException{
Date start=new Date();
System.out.println("Future Start time :: "+start);
List<Future<String>> futureList=new ArrayList<Future<String>>();
CallableTest callableTest=null;
ResultClassTest resultClassTest=new ResultClassTest();
for (int i = 0; i < 3; i++) {
callableTest=new CallableTest();
callableTest.setThreadWork(""+i);
callableTest.setResultClassTest(resultClassTest);
Future<String> future=threadpool.submit(callableTest);
futureList.add(future);
}
threadpool.shutdown();
for (Future<String> future : futureList) {
System.out.println("time to done by every thread :: "+future.get()+" "+new Date());
}
System.out.println("result in Test future Result1 :: "+callableTest.getResultClassTest().getResult1());
System.out.println("result in Test future Result2 :: "+callableTest.getResultClassTest().getResult2());
System.out.println("result in Test future Result3 :: "+callableTest.getResultClassTest().getResult3());
Date end=new Date();
System.out.println("Future End time :: "+end);
System.out.println("Difference Future :: "+((end.getTime()-start.getTime())/1000));
}
}
import java.util.concurrent.Callable;
public class CallableTest implements Callable<String> {
private String threadWork;
private String result;
private ResultClassTest resultClassTest;
public String getThreadWork() {
return threadWork;
}
public void setThreadWork(String threadWork) {
this.threadWork = threadWork;
}
public String getResult() {
return result;
}
public void setResult(String result) {
this.result = result;
}
public ResultClassTest getResultClassTest() {
return resultClassTest;
}
public void setResultClassTest(ResultClassTest resultClassTest) {
this.resultClassTest = resultClassTest;
}
@Override
public String call() throws Exception {
if(threadWork!=null){
if(threadWork.equals("0")){
this.getResultClassTest().setResult1(this.getFirstOutput());
this.setResult("one");
}else if(threadWork.equals("1")){
this.getResultClassTest().setResult2(this.getSecondOutput());
this.setResult("two");
}else if(threadWork.equals("2")){
this.getResultClassTest().setResult3(this.getThirdOutput());
this.setResult("three");
}
}
return result;
}
private Long getThirdOutput() {
System.out.println("In Third");
Long a=0l;
for (long i = 400001; i < 600000000l; i++) {
a+=i;
}
for (long i = 200001; i < 400000000l; i++) {
a+=i;
}
for (long i = 200001; i < 400000000l; i++) {
a+=i;
}
System.out.println("three "+a);
return a;
}
private Long getSecondOutput() {
System.out.println("In Second");
Long a=0l;
for (long i = 200001; i < 400000000l; i++) {
a+=i;
}
for (long i = 200001; i < 400000000l; i++) {
a+=i;
}
for (long i = 200001; i < 400000000l; i++) {
a+=i;
}
System.out.println("two "+a);
return a;
}
private Long getFirstOutput() {
System.out.println("In First");
Long a=0l;
for (long i = 0; i < 200000000l; i++) {
a+=i;
}
for (long i = 200001; i < 400000000l; i++) {
a+=i;
}
for (long i = 200001; i < 400000000l; i++) {
a+=i;
}
System.out.println("one "+a);
return a;
}
}
public class ResultClassTest {
private Long result1;
private Long result2;
private Long result3;
public Long getResult1() {
return result1;
}
public void setResult1(Long result1) {
this.result1 = result1;
}
public Long getResult2() {
return result2;
}
public void setResult2(Long result2) {
this.result2 = result2;
}
public Long getResult3() {
return result3;
}
public void setResult3(Long result3) {
this.result3 = result3;
}
}
public class TestLinear {
public Long getThirdOutput() {
System.out.println("In Third");
Long a=0l;
for (long i = 400001; i < 600000000l; i++) {
a+=i;
}
for (long i = 200001; i < 400000000l; i++) {
a+=i;
}
for (long i = 200001; i < 400000000l; i++) {
a+=i;
}
System.out.println("three "+a);
return a;
}
public Long getSecondOutput() {
System.out.println("In Second");
Long a=0l;
for (long i = 200001; i < 400000000l; i++) {
a+=i;
}
for (long i = 200001; i < 400000000l; i++) {
a+=i;
}
for (long i = 200001; i < 400000000l; i++) {
a+=i;
}
System.out.println("two "+a);
return a;
}
public Long getFirstOutput() {
System.out.println("In First");
Long a=0l;
for (long i = 0; i < 200000000l; i++) {
a+=i;
}
for (long i = 200001; i < 400000000l; i++) {
a+=i;
}
for (long i = 200001; i < 400000000l; i++) {
a+=i;
}
System.out.println("one "+a);
return a;
}
}
該測試包括四個類如TestFuture（主類），CallableTest（它實現可贖回接口），ResultClassTest（對併發執行結果類）和TestLinear（用於線性執行）。如果我做錯了什麼，請告訴我。
在此先感謝。
感謝您的回覆，我明白了您的觀點，並在毫秒內也做到了這一點。以毫秒爲單位的差異，但我希望差不多3至4秒的差異，但它不是同一種類型的，這就是爲什麼我要求它。 –
你可能想看看這個線程：http://stackoverflow.com/questions/1647990/executorservices-surprising-performance-break-even-point-rules-of-thumb。基本上，需要考慮線程池的開銷成本。 – Chill
嗨寒意，我已經審查過，並檢查代碼，但無法找到任何太多的差異。將再次檢查並回復給你。 –