首先这里是代码,你可以只复制一个粘贴
import java.util.ArrayList;
public class RepetionCounter implements Runnable{
private int x;
private int y;
private int[][] matrix;
private int xCounter;
private int yCounter;
private ArrayList<Thread> threadArray;
private int rowIndex;
private boolean[] countCompleted;
public RepetionCounter(int x, int y, int [][]matrix)
{
this.x = x;
this.y = y;
this.matrix = matrix;
this.threadArray = new ArrayList<Thread>(matrix.length);
this.rowIndex = 0;
for(int i = 0; i < matrix.length; i++){
threadArray.add(new Thread(this));
}
countCompleted = new boolean[matrix.length];
}
public void start(){
for (int i = 0; i < threadArray.size(); i++){
threadArray.get(i).start();
this.rowIndex++;
}
}
public void count(int rowIndex)
{
for(int i = 0; i < matrix[rowIndex].length; i++){
if (matrix[rowIndex][i] == x){
this.xCounter++;
} else if (matrix[rowIndex][i] == y){
this.yCounter++;
}
}
}
@Override
public void run() {
count(this.rowIndex);
countCompleted[this.rowIndex] = true;
}
public int getxCounter() {
return xCounter;
}
public void setxCounter(int xCounter) {
this.xCounter = xCounter;
}
public int getyCounter() {
return yCounter;
}
public void setyCounter(int yCounter) {
this.yCounter = yCounter;
}
public boolean[] getCountCompleted() {
return countCompleted;
}
public void setCountCompleted(boolean[] countCompleted) {
this.countCompleted = countCompleted;
}
public static void main(String args[]){
int[][] matrix = {{0,2,1}, {2,3,4}, {3,2,0}};
RepetionCounter rc = new RepetionCounter(0, 2, matrix);
rc.start();
boolean ready = false;
while(!ready){
for(int i = 0; i < matrix.length; i++){
if (rc.getCountCompleted()[i]){
ready = true;
} else {
ready = false;
}
}
}
if (rc.getxCounter() > rc.getyCounter()){
System.out.println("Thre are more x than y");
} else {System.out.println("There are:"+rc.getxCounter()+" x and:"+rc.getyCounter()+" y");
}
}
}
我想要这个代码做什么:我给对象一个矩阵和两个数字,我想知道这两个数字出现在矩阵中的次数。我创建了与矩阵的行数一样多的线程('为什么有那个ArrayList',所以在这个对象中我有k个线程(假设k是行数),每个都计算两个的出现次数数字。 问题是:如果我第一次运行它一切正常,但如果我再次尝试执行它而得到IndexOutOfBoundException,或者发生错误计数,奇怪的是如果我得到错误,并修改代码,之后它将再次工作一次。 你能解释一下为什么会这样吗?
答案 0 :(得分:2)
您需要为每个线程提供自己的Runnable。让他们共享相同的Runnable将导致灾难性的竞争条件。将每个线程需要做的逻辑分离到Runnable中。然后将启动线程的代码部分移动到Runnable之外的位置。
BTW查看java.util.concurrent包中的Executors,你不必为这些东西使用原始线程。同样使用Executors可能会让您更好地了解将Task中的内容与其他内容分开。
答案 1 :(得分:2)
您为每个帖子使用相同的RepetitionCounter
实例:
for(int i = 0; i < matrix.length; i++){
threadArray.add(new Thread(this));
}
所以他们将共享相同的rowIndex
。这段代码非常令人困惑,所以我建议你将线程的逻辑封装在一个单独的Runnable
类中,并带有各个行ID:
class ThreadTask implements Runnable {
private int rowId;
private int[][] matrix;
public ThreadTask(int[][] matrix, int rowId) {
this.matrix = matrix; // only a reference is passed here so no worries
this.rowId = rowId;
}
public void run() {
// search on my row
}
}
然后:
for(int i = 0; i < matrix.length; i++) {
threadArray.add(new Thread(new ThreadTask(matrix, i)));
}