Java中的 DigestInputStream getMessageDigest() 方法及示例

Java.security.DigestInputStream类的getMessageDigest()方法提供了分配给此DigestInputStream 对象的MessageDigest。

句法：

public MessageDigest getMessageDigest()

返回值：此方法返回分配给它的 MessageDigest 对象。

注意：本文中的所有程序都不会在在线 IDE 上运行，因为不存在“名称”文件。您可以在系统上的Java编译器上检查此代码。要检查此代码，请在您的系统上创建一个文件“名称”。

以下是说明getMessageDigest()方法的示例：

示例 1：

Java

// Java program to demonstrate
// getInstance() method
 
import java.security.*;
import java.util.*;
import java.io.*;
 
public class GFG {
    public static void main(String[] argv)
    {
        try {
            // creating the object of MessageDigest
            // and getting instance
            // By using getInstance() method
            MessageDigest sr
                = MessageDigest.getInstance("MD5");
 
            // creating and initializing
            // object of InputStream
            InputStream is
                = new FileInputStream("f:/java/name.txt");
 
            // creating and initializing
            // object of DigestInputStream
            DigestInputStream di
                = new DigestInputStream(is, sr);
 
            // getting the message digest
            // using getMessageDigest() method
            MessageDigest str = di.getMessageDigest();
 
            // display the result
            System.out.println("Status : " + str.toString());
        }
 
        catch (NoSuchAlgorithmException e) {
 
            System.out.println("Exception thrown : " + e);
        }
        catch (NullPointerException e) {
 
            System.out.println("Exception thrown : " + e);
        }
        catch (FileNotFoundException e) {
 
            System.out.println("Exception thrown : " + e);
        }
    }
}

输出：

Status : MD5 Message Digest from SUN, 

示例 2：

Java

// Java program to demonstrate
// getInstance() method
 
import java.security.*;
import java.util.*;
import java.io.*;
 
public class GFG {
    public static void main(String[] argv)
    {
        try {
            // creating the object of MessageDigest
            // and getting instance
            // By using getInstance() method
            MessageDigest sr
                = MessageDigest.getInstance("SHA-1");
 
            // creating and initializing
            // object of InputStream
            InputStream is
                = new FileInputStream("f:/java/name.txt");
 
            // creating and initializing// object of DigestInputStream
                DigestInputStream di
                = new DigestInputStream(is, sr);
 
            // getting the message digest
            // using getMessageDigest() method
            MessageDigest str = di.getMessageDigest();
 
            // printing the status
            System.out.println("Status : " + str.toString());
        }
 
        catch (NoSuchAlgorithmException e) {
 
            System.out.println("Exception thrown : " + e);
        }
        catch (NullPointerException e) {
 
            System.out.println("Exception thrown : " + e);
        }
        catch (FileNotFoundException e) {
 
            System.out.println("Exception thrown : " + e);
        }
    }
}

输出：

Status : SHA-1 Message Digest from SUN, 

参考： https://docs.oracle.com/javase/9/docs/api/ Java/security/DigestInputStream.html#getMessageDigest–