通過多個執行緒并行計算哈希并將輸出添加到ArrayList<String>

我撰寫了以下代碼以計算 a 的哈希值String（基于 SHA-256），然后將所有輸出插入到 a 中ArrayList<String>：

        ArrayList<Thread> threadList = new ArrayList<Thread>();
        ArrayList<String> threadListStr = new ArrayList<String>();
        int threadNumber = 100;
        for (int i = 0; i < threadNumber; i  ) {
            String tId = String.valueOf(i);
            Thread thr = new Thread(() -> {
                threadListStr.add(calculateHash(tId));
            });
            threadList.add(thr);
        }

        // START the threads
        for (int i = 0; i < threadNumber; i  ) {
            threadList.get(i).start();
        }
        // STOP the threads
        for (int i = 0; i < threadNumber; i  ) {
            threadList.get(i).interrupt();
        }

        System.out.println("Size of ArrayList<String> is: "   threadListStr.size());
        System.out.println("Size of ArrayList<Thread> is: "   threadList.size());
        
        /////////////////////
        
        public static String calculateHash(String tId) {
        String tIdStr = org.apache.commons.codec.digest.DigestUtils.sha256Hex(tId);
        return tIdStr;
        }

但是，ArrayList 并沒有變得完整，正如您在運行 5 次代碼后看到的那樣，每次 ArrayList 都有不同的大小（盡管 ArrayList threadList 始終是完整的，因為執行緒數為 100。）

//1th run
Size of ArrayList<String> is: 60
Size of ArrayList<Thread> is: 100

//2nd run
Size of ArrayList<String> is: 30
Size of ArrayList<Thread> is: 100

//3rd run
Size of ArrayList<String> is: 10
Size of ArrayList<Thread> is: 100

//4th run
Size of ArrayList<String> is: 61
Size of ArrayList<Thread> is: 100

//5th
Size of ArrayList<String> is: 69
Size of ArrayList<Thread> is: 100

應該如何修改代碼以完整ArrayList<String>存盤所有輸出？

編輯：我按如下方式更改了代碼，但輸出是相同的。

        ArrayList<Thread> threadList = new ArrayList<Thread>();
        //ArrayList<String> threadListStr = new ArrayList<String>();
        List<String> threadListStrSync = Collections.synchronizedList(new ArrayList<>());
        int threadNumber = 100;
        for (int i = 0; i < threadNumber; i  ) {
            String tId = String.valueOf(i);
            Thread thr = new Thread(() -> {
                threadListStrSync.add(calculateHash(tId));
            });
            threadList.add(thr);
        }

        // START the threads
        for (int i = 0; i < threadNumber; i  ) {
            threadList.get(i).start();
        }
        // STOP the threads
        for (int i = 0; i < threadNumber; i  ) {
            threadList.get(i).interrupt();
        }

        System.out.println("Size of ArrayList<String> is: "   threadListStrSync.size());
        System.out.println("Size of ArrayList<Thread> is: "   threadList.size());

注意：我評論了，interrupt();但輸出仍然相同。

uj5u.com熱心網友回復：

有多個問題

1. 使用執行緒安全集合或手動同步訪問 - 一個簡單的選擇是用 Collections.synchronizedList()
2. interrupt()不需要，執行緒將在到達其run()-method的末尾時終止
3. 您需要等待所有執行緒在列印結果之前終止 - 要做到這一點，呼叫join()而不是interrupt()

uj5u.com熱心網友回復：

您有兩個問題：1) 可能有些執行緒在執行程序中永遠無法將其哈希 ID 添加到集合中，以及 2) 多個執行緒正在訪問哈希 ID 的集合，因此您應該使用執行緒安全的集合.

    ArrayList<Thread> threadList = new ArrayList<Thread>();
    Collection<String> threadListStr = Collections.synchronizedCollection( new ArrayList<String>() );
    int threadNumber = 100;
    for (int i = 0; i < threadNumber; i  ) {
        String tId = String.valueOf(i);
        Thread thr = new Thread(() -> {
            threadListStr.add(calculateHash(tId));
        });
        threadList.add(thr);
    }

    // START the threads
    for (int i = 0; i < threadNumber; i  ) {
        threadList.get(i).start();
    }
    // STOP the threads
    for (int i = 0; i < threadNumber; i  ) {
       try {
           threadList.get(i).join();
       } catch( InterruptedException exc ) {
           // handle interrupted exception
       }
    }

    System.out.println("Size of ArrayList<String> is: "   threadListStr.size());
    System.out.println("Size of ArrayList<Thread> is: "   threadList.size());
    

標籤：爪哇 多线程 数组列表 并发

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