[問題] java多執行緒問題請教

[doggingg (doggingg)]

我想自行練習寫一個多執行緒，
讓args吃兩個參數-一個決定動態生成幾個Thread-一個是整數N
把整數N平分給每個Thread去計算總和最後再把所有Thread算好的部分加總起來
但我的程式遇到一點問題，
我希望呼叫check方法時可以取得所有thread算完的總和，請問該怎麼做呢?????

public class Project {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        // TODO code application logic here


        String temp1="";
        String temp2="";
        int ThreadNum=0;
        int n=0;
        temp1 = args[0];
        temp2 = args[1];
        ThreadNum = Integer.parseInt(temp1);
        n = Integer.parseInt(temp2);
        Show ba = new Show();

        Counting[] p = new Counting[ThreadNum+1];
        Thread[] t = new Thread[p.length];
        int total =0;
        for(int i=1;i<p.length;i++)
        {
            int m = (i-1)*(n/ThreadNum)+1;
            int s = i*(n/ThreadNum);
            String Name = "t["+i+"]";
            p[i] = new Counting(ba,Name,m,s);
            t[i] = new Thread(p[i]);

            t[i].start();
            System.out.println(ba.total);
        }

        //System.out.println();

        //System.out.println("temp="+temp);

    }

}
class Show
{
    public static int total ;
    public static int last =total;
    public void save(int x)
    {
        total+=x;
        //System.out.println("now total:"+total);
    }
    public void check()
    {
        System.out.println(total);
        //return total;
    }

}

class Counting implements Runnable
{
    private int start;
    private int end;
    public int sum;
    private String name;
    Show ba;
    public int temp=0;

    Counting (Show ba,String n,int m,int s)
    {
        this.ba = ba;
        name = n;
        start = m;
        end = s;
    }
        public synchronized void run()
        {
            System.out.println(name+"\tstarting");
            for(int a = start;a<=end;a++)
            {
                sum+=a;
            }
            //System.out.println(t[0].current.getName());
            //System.out.println(start+"\t"+end+"\t"+sum);
            //System.out.println("-----------------");

            ba.save(sum);
            temp = sum;
            //System.out.println(ba.check());
            ba.check();
            System.out.println(name+"\tover");
        }


}

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◆ From: 140.121.196.35
推 swpoker:你在show那邊做一個計數的就可以了
→ doggingg:有阿，可是我要怎麼才能在所有THREAD執行完後再取結果值
推 LaPass:丟個block卡住他，另外thing in java有講另外一種，專門為
推 LaPass:計算=>取值用的執行緒物件，不過我手邊沒書....
推 Chikei:CountDownLatch
推 mars90226:wait()執行緒?
→ doggingg:謝謝大家~我作好了
→ H45:做完了？我看這程式有Race Condition，也解決了嗎？
推 PsMonkey:違反版規 4.1，鎖文軟性懲罰
→ PsMonkey:講錯了，是 4.2 XD
→ doggingg:恩~在下方補上join就可以同步了，謝謝