ADD file via upload

comment_tree.java

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+import java.nio.charset.StandardCharsets;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.util.ArrayList;
+import java.util.List;
+
+class MerkleNode {
+    private String hash;
+    private MerkleNode left;
+    private MerkleNode right;
+
+    public MerkleNode(String hash) {
+        this.hash = hash;
+        this.left = null;
+        this.right = null;
+    }
+
+    public String getHash() {
+        return hash;
+    }
+
+    public MerkleNode getLeft() {
+        return left;
+    }
+
+    public void setLeft(MerkleNode left) {
+        this.left = left;
+    }
+
+    public MerkleNode getRight() {
+        return right;
+    }
+
+    public void setRight(MerkleNode right) {
+        this.right = right;
+    }
+}
+
+public class MerkleTree {
+    private MerkleNode root;
+
+    public MerkleTree(List<String> data) {
+        this.root = buildTree(data);
+    }
+
+    public MerkleNode getRoot() {
+        return root;
+    }
+
+    private MerkleNode buildTree(List<String> data) {
+        List<MerkleNode> nodes = new ArrayList<>();
+
+        for (String value : data) {
+            String hash = calculateHash(value);
+            nodes.add(new MerkleNode(hash));
+        }
+
+        while (nodes.size() > 1) {
+            List<MerkleNode> tempNodes = new ArrayList<>();
+
+            for (int i = 0; i < nodes.size(); i += 2) {
+                MerkleNode left = nodes.get(i);
+                MerkleNode right = (i + 1 < nodes.size()) ? nodes.get(i + 1) : null;
+                String concatHash = left.getHash() + ((right != null) ? right.getHash() : "");
+                String parentHash = calculateHash(concatHash);
+                MerkleNode parent = new MerkleNode(parentHash);
+                parent.setLeft(left);
+                parent.setRight(right);
+                tempNodes.add(parent);
+            }
+
+            nodes = tempNodes;
+        }
+
+        return nodes.get(0);
+    }
+
+    private String calculateHash(String data) {
+        try {
+            MessageDigest digest = MessageDigest.getInstance("SHA-256");
+            byte[] hash = digest.digest(data.getBytes(StandardCharsets.UTF_8));
+            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();
+        } catch (NoSuchAlgorithmException e) {
+            e.printStackTrace();
+        }
+
+        return null;
+    }
+
+    public static void main(String[] args) {
+        List<String> data = new ArrayList<>();
+        data.add("Comment 1");
+        data.add("Comment 2");
+        data.add("Comment 3");
+        data.add("Comment 4");
+        data.add("Private Key");
+        data.add("Like Count");
+
+        MerkleTree merkleTree = new MerkleTree(data);
+        MerkleNode root = merkleTree.getRoot();
+
+        printMerkleTree(root, 0);
+    }
+
+    private static void printMerkleTree(MerkleNode root, int level) {
+        if (root == null) {
+            return;
+        }
+
+        for (int i = 0; i < level; i++) {
+            System.out.print("  ");
+        }
+
+        System.out.println("|-- " + root.getHash());
+
+        printMerkleTree(root.getLeft(), level + 1);
+        printMerkleTree(root.getRight(), level + 1);
+    }
+}
+/*这个程序定义了一个MerkleNode类表示梅克尔树中的节点，并提供了用于获取哈希值和子节点的方法。MerkleTree类构建了梅克尔树，并提供了获取根节点的方法。程序中的calculateHash方法使用SHA-256算法计算数据的哈希值。
+
+在main方法中，创建一个包含评论索引、评论哈希、私钥签名和点赞数的数据列表，并使用该数据构建一个梅克尔树。然后，打印出整个梅克尔树的结构。*/