区块链java代码实现

package test;
import java.security.MessageDigest;
import java.util.ArrayList;
import java.util.List;
public class MerkleTrees {
  // transaction List
  List<String> txList;
  // Merkle Root
  String root;

  /**
  * constructor
  * @param txList transaction List 交易List
  */
  public MerkleTrees(List<String> txList) {
  this.txList = txList;
  root = "";
  }

  /**
  * execute merkle_tree and set root.
  */
  public void merkle_tree() {

  List<String> tempTxList = new ArrayList<String>();

  for (int i = 0; i < this.txList.size(); i++) {
   tempTxList.add(this.txList.get(i));
  }

  List<String> newTxList = getNewTxList(tempTxList);

  while (newTxList.size() != 1) {
   newTxList = getNewTxList(newTxList);
  }

  this.root = newTxList.get(0);
  }

  /**
  * return Node Hash List.
  * @param tempTxList
  * @return
  */
  private List<String> getNewTxList(List<String> tempTxList) {

  List<String> newTxList = new ArrayList<String>();
  int index = 0;
  while (index < tempTxList.size()) {
   // left
   String left = tempTxList.get(index);
   index++;
   // right
   String right = "";
   if (index != tempTxList.size()) {
   right = tempTxList.get(index);
   }
   // sha2 hex value
   String sha2HexValue = getSHA2HexValue(left + right);
   newTxList.add(sha2HexValue);
   index++;

  }

  return newTxList;
  }

  /**
  * Return hex string
  * @param str
  * @return
  */
  public String getSHA2HexValue(String str) {
   byte[] cipher_byte;
   try{
    MessageDigest md = MessageDigest.getInstance("SHA-256");
    md.update(str.getBytes());
    cipher_byte = md.digest();
    StringBuilder sb = new StringBuilder(2 * cipher_byte.length);
    for(byte b: cipher_byte) {
     sb.append(String.format("%02x", b&0xff) );
    }
    return sb.toString();
   } catch (Exception e) {
     e.printStackTrace();
   }

   return "";
  }

  /**
  * Get Root
  * @return
  */
  public String getRoot() {
  return this.root;
  }

 }

List<String> tempTxList = new ArrayList<String>();
tempTxList.add("a");
tempTxList.add("b");
tempTxList.add("c");
tempTxList.add("d");
tempTxList.add("e");

private List<String> getNewTxList(List<String> tempTxList) {
 List<String> newTxList = new ArrayList<String>();
 int index = 0;
 while (index < tempTxList.size()) {
  // left
  String left = tempTxList.get(index);
  index++;
  // right
  String right = "";
  if (index != tempTxList.size()) {
   right = tempTxList.get(index);
  }
  // sha2 hex value
  String sha2HexValue = getSHA2HexValue(left + right);
  newTxList.add(sha2HexValue);
  index++;
 }

package test;
import java.util.ArrayList;
import java.util.List;
public class App {
   public static void main(String [] args) {
    List<String> tempTxList = new ArrayList<String>();
    tempTxList.add("a");
    tempTxList.add("b");
    tempTxList.add("c");
    tempTxList.add("d");
    tempTxList.add("e");

    MerkleTrees merkleTrees = new MerkleTrees(tempTxList);
    merkleTrees.merkle_tree();
    System.out.println("root : " + merkleTrees.getRoot());
   }
  }