Update README.md Add ThreadSafeHashing class for concurrent SHA-256 hashing in Java

README.md

@@ -1,2 +1,52 @@
 # PRReview
 PRReview Project
+
+add Java Code
+
+
+```Java
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
+public class ThreadSafeHashing {
+
+    private static final ConcurrentHashMap<String, String> hashMap = new ConcurrentHashMap<>();
+
+    public static void main(String[] args) {
+        ExecutorService executorService = Executors.newFixedThreadPool(10); // 创建一个固定大小的线程池
+
+        String[] data = {"data1", "data2", "data3", "data4", "data5"}; // 待加密数据
+
+        for (String item : data) {
+            executorService.submit(() -> {
+                try {
+                    String hash = hashData(item);
+                    hashMap.put(item, hash); // 将哈希值保存到ConcurrentHashMap中
+                    System.out.println("Data: " + item + " Hash: " + hash);
+                } catch (NoSuchAlgorithmException e) {
+                    e.printStackTrace();
+                }
+            });
+        }
+
+        executorService.shutdown(); // 关闭线程池
+    }
+
+    private static String hashData(String data) throws NoSuchAlgorithmException {
+        MessageDigest digest = MessageDigest.getInstance("SHA-256"); // 使用SHA-256算法
+        byte[] hash = digest.digest(data.getBytes());
+        StringBuilder hexString = new StringBuilder();
+        for (byte b : hash) {
+            String hex = Integer.toHexString(0xff & b);
+            if (hex.length() == 1) {
+                hexString.append('0');
+            }
+            hexString.append(hex);
+        }
+        return hexString.toString(); // 返回哈希值的十六进制字符串表示
+    }
+}
+```