Java DigestInputStream getMessageDigest()方法及示例

java.security.DigestInputStream 类的 getMessageDigest() 方法提供分配给这个DigestInputStream对象的MessageDigest。

语法

public MessageDigest getMessageDigest()

返回值： 该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，因为没有’name’文件存在。你可以在你的系统的Java编译器上检查这段代码。为了检查这段代码，在你的系统上创建一个’name’文件。

下面是说明 getMessageDigest() 方法的例子。

例1 :

// 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,

例2 :

// 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