即使数据集更改为另一个值，哈希也不会改变

Question

我用 java 创建了简单的区块链程序。目前我正在为交易数据集生成哈希。当我更改交易数据集时，哈希值没有改变

首先，我创建了一个交易 class，其中包含交易名称、交易 ID 和交易时间戳值。目前 transactionDate 和 transactionID 是自动生成的。

这是包裹MainNode.pkg;

import NodeData.pkg.TransactionClass;
import sun.util.logging.PlatformLogger;

import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * @author melanrashitha
 * @date 11/12/19
 * @project BlockChainArchController
 */
public class MainNode {

        private int hash;
        private int prevHash;
        private TransactionClass[] transactionData;
        Logger logger = Logger.getLogger("MainNode");

    public MainNode(int prevHash, TransactionClass[] transactionData) {

        //Logger MainNode Transaction class init
        logger.log(Level.INFO,"Node HB Received");


        this.prevHash = prevHash;
        logger.log(Level.INFO,"Node prevHash loaded : "+prevHash);

        this.transactionData = transactionData;

        logger.log(Level.INFO,"Node HB Received");
        logger.log(Level.INFO,"Node transactionData loaded : "+transactionData);




        //Current Calculated blockhash calculated on current transaction data, prev hashcode
        logger.log(Level.INFO,"Node Hash Generating ");
        Object[] object = new Object[] {transactionData,prevHash};

        this.hash = object.hashCode();
        logger.log(Level.INFO,"Node Hash Generated  :  "+ this.hash);
        logger.log(Level.INFO,"Node HB Detached");
    }

    public int getHash() {
        return hash;
    }

    public int getPrevHash() {
        return prevHash;
    }

    public TransactionClass[] getTransactionData() {
        return transactionData;
    }
}

当交易数据改变时它仍然显示相同的散列值

这是日志消息

/Library/Java/JavaVirtualMachines/jdk1.8.0_212.jdk/Contents/Home/bin/java "-javaagent:/Applications/IntelliJ IDEA.app/Contents/lib/idea_rt.jar=55843:/Applications/IntelliJ IDEA.app/Contents/bin" -Dfile.encoding=UTF-8 -classpath /Library/Java/JavaVirtualMachines/jdk1.8.0_212.jdk/Contents/Home/jre/lib/charsets.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_212.jdk/Contents/Home/jre/lib/deploy.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_212.jdk/Contents/Home/jre/lib/ext/cldrdata.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_212.jdk/Contents/Home/jre/lib/ext/dnsns.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_212.jdk/Contents/Home/jre/lib/ext/jaccess.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_212.jdk/Contents/Home/jre/lib/ext/jfxrt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_212.jdk/Contents/Home/jre/lib/ext/localedata.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_212.jdk/Contents/Home/jre/lib/ext/nashorn.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_212.jdk/Contents/Home/jre/lib/ext/sunec.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_212.jdk/Contents/Home/jre/lib/ext/sunjce_provider.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_212.jdk/Contents/Home/jre/lib/ext/sunpkcs11.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_212.jdk/Contents/Home/jre/lib/ext/zipfs.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_212.jdk/Contents/Home/jre/lib/javaws.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_212.jdk/Contents/Home/jre/lib/jce.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_212.jdk/Contents/Home/jre/lib/jfr.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_212.jdk/Contents/Home/jre/lib/jfxswt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_212.jdk/Contents/Home/jre/lib/jsse.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_212.jdk/Contents/Home/jre/lib/management-agent.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_212.jdk/Contents/Home/jre/lib/plugin.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_212.jdk/Contents/Home/jre/lib/resources.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_212.jdk/Contents/Home/jre/lib/rt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_212.jdk/Contents/Home/lib/ant-javafx.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_212.jdk/Contents/Home/lib/dt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_212.jdk/Contents/Home/lib/javafx-mx.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_212.jdk/Contents/Home/lib/jconsole.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_212.jdk/Contents/Home/lib/packager.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_212.jdk/Contents/Home/lib/sa-jdi.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_212.jdk/Contents/Home/lib/tools.jar:/Users/melanrashitha/Desktop/Desktop/stripe-payment-gateway-module/BlockChainArchController/out/production/BlockChainArchController MainNode.pkg.BlockChainMain
Nov 12, 2019 11:57:02 AM NodeData.pkg.TransactionClass <init>
INFO: Transaction HB Recieved
Nov 12, 2019 11:57:02 AM NodeData.pkg.TransactionClass setTransactionDate
INFO: Transaction Date Created : 15068497599682
Nov 12, 2019 11:57:02 AM NodeData.pkg.TransactionClass setTransactionID
INFO: TransactionID Created : 64c27bf9-d3e6-48bc-b2b5-d6cc10f62df7
Nov 12, 2019 11:57:02 AM NodeData.pkg.TransactionClass <init>
INFO: Transaction HB Detached
Nov 12, 2019 11:57:02 AM NodeData.pkg.TransactionClass <init>
INFO: Transaction HB Recieved
Nov 12, 2019 11:57:02 AM NodeData.pkg.TransactionClass setTransactionDate
INFO: Transaction Date Created : 15068523666838
Nov 12, 2019 11:57:02 AM NodeData.pkg.TransactionClass setTransactionID
INFO: TransactionID Created : 9796a6c7-9d74-404a-8434-9844c18e481a
Nov 12, 2019 11:57:02 AM NodeData.pkg.TransactionClass <init>
INFO: Transaction HB Detached
Nov 12, 2019 11:57:02 AM NodeData.pkg.TransactionClass <init>
INFO: Transaction HB Recieved
Nov 12, 2019 11:57:02 AM NodeData.pkg.TransactionClass setTransactionDate
INFO: Transaction Date Created : 15068528416745
Nov 12, 2019 11:57:02 AM NodeData.pkg.TransactionClass setTransactionID
INFO: TransactionID Created : 9469aa4e-70fb-4088-9261-a5274f4214fc
Nov 12, 2019 11:57:02 AM NodeData.pkg.TransactionClass <init>
INFO: Transaction HB Detached
Nov 12, 2019 11:57:02 AM NodeData.pkg.TransactionClass <init>
INFO: Transaction HB Recieved
Nov 12, 2019 11:57:02 AM NodeData.pkg.TransactionClass setTransactionDate
INFO: Transaction Date Created : 15068533175911
Nov 12, 2019 11:57:02 AM NodeData.pkg.TransactionClass setTransactionID
INFO: TransactionID Created : 1d179fc7-eb39-4c81-bfed-4afdb8579a8f
Nov 12, 2019 11:57:02 AM NodeData.pkg.TransactionClass <init>
INFO: Transaction HB Detached
Nov 12, 2019 11:57:02 AM MainNode.pkg.MainNode <init>
INFO: Node HB Received
Nov 12, 2019 11:57:02 AM MainNode.pkg.MainNode <init>
INFO: Node prevHash loaded : 1
Nov 12, 2019 11:57:02 AM MainNode.pkg.MainNode <init>
INFO: Node HB Received
Nov 12, 2019 11:57:02 AM MainNode.pkg.MainNode <init>
INFO: Node transactionData loaded : [LNodeData.pkg.TransactionClass;@5caf905d
Nov 12, 2019 11:57:02 AM MainNode.pkg.MainNode <init>
INFO: Node Hash Generating `enter code here`
Nov 12, 2019 11:57:02 AM MainNode.pkg.MainNode <init>
INFO: Node Hash Generated  :  41359092
Nov 12, 2019 11:57:02 AM MainNode.pkg.MainNode <init>
INFO: Node HB Detached

Answer 1

问题是您在数组上调用 hashCode()，在您的例子中是 Object[] object。由于数组不会覆盖对象 class 中的 hashCode() 方法，因此您将从 Object.hashCode() 方法中获得结果。此方法不会考虑数组的内容。因此，在您当前的 JRE 中，您每次都会获得相同的数组哈希码。

String[] data = new String[2];
System.out.println(Arrays.toString(data)+" - "+data.hashCode());
data[0] = "abc";
System.out.println(Arrays.toString(data)+" - "+data.hashCode());
data[1] = "def";
System.out.println(Arrays.toString(data)+" - "+data.hashCode());

这将生成类似于此的输出：

[null, null] - 705927765
[abc, null] - 705927765
[abc, def] - 705927765

如您所见，即使我们更改其内容，哈希码也没有变化。要解决此问题，您可以使用 Arrays.deepHashCode() 方法。它将 return 基于数组内容的哈希码。通过运行下面的代码试试看：

String[] data = new String[2];
System.out.println(Arrays.toString(data)+" - "+Arrays.deepHashCode(data));
data[0] = "abc";
System.out.println(Arrays.toString(data)+" - "+Arrays.deepHashCode(data));
data[1] = "def";
System.out.println(Arrays.toString(data)+" - "+Arrays.deepHashCode(data));

您将得到以下输出：

[null, null] - 961
[abc, null] - 2987935
[abc, def] - 3087268

请记住，您的 TransactionClass class 必须覆盖 hashCode() 方法才能使其正常工作。另请记住，当您覆盖 hashCode() 方法时，您可能还需要覆盖 equals() 方法。

即使数据集更改为另一个值，哈希也不会改变

Hash does not change even when data set is changed to another value

java

arrays

java-8

blockchain

hashcode