我的作业是使用并行化创建项目,一切都应该是正确的。但是,我做了我的项目,但我的教授在我的代码中提到了一些错误“请查看数组列表,有些东西不对,也许是同步?”。
我想请你们社区帮助我并指出可能出了什么问题。我认为没有用synchronize
括号覆盖我的数组列表可能是个问题,对吗?
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.logging.Level;
import java.util.logging.Logger;
/**
* My project finds all dividors for specific number
*It must use threads, so I made them. First I start them (first loop)
*then join them (second loop). My project must have that loops.
*Problem might be with not synchronizing methods array list...
*/
public class Main {
private final static int NUMBER = 100;
private final static List<Integer> dividors = new ArrayList<Integer>();
public static void main(String[] args) {
new Main().doStuff();
}
private int sqr;
private int sqrp1;
private void doStuff() {
sqr = (int) Math.sqrt(NUMBER);
sqrp1 = sqr + 1;
Thread[] t = new Thread[sqrp1];
//starting tasks
for (int i = 1; i < sqrp1; i++) {
final int it = i;
if (NUMBER % i == 0) {
final int e = i;
t[i] = new Thread(new Runnable() {
@Override
public void run() {
System.out.println("sta"+e);
if (!checkContains(e)) {
addElement(e);
}
final int dividednumber = NUMBER / e;
if (!checkContains(dividednumber)) {
addElement(dividednumber);
}
}
});
t[i].start();
}
}
//calling join for tasks
for (int i = 1; i < sqrp1; i++) {
final int it = i;
if (NUMBER % i == 0) {
try {
System.out.println("sto"+i);
t[i].join();
} catch (InterruptedException ex) {
Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
System.out.println("xxx");
Collections.sort(dividors);
Integer[] arrayDividors = dividors.toArray(new Integer[0]);
for (int i = 0; i < arrayDividors.length; i++) {
System.out.println(arrayDividors[i]);
}
}
private synchronized void addElement(int element) {
dividors.add(element);
}
private synchronized boolean checkContains(int element) {
return dividors.contains(element);
}
}
我更改这部分是否正确,现在可以吗?
t[i] = new Thread(new Runnable() {
@Override
public void run() {
System.out.println("waiting " + e);
synchronized (this) {
System.out.println("entering " + e);
if (!checkContains(e)) {
addElement(e);
}
final int dividednumber = NUMBER / e;
if (!checkContains(dividednumber)) {
addElement(dividednumber);
}
System.out.println("leaving " + e);
}
}
});