Java 中的 MessageDigest getInstance()方法，带示例

原文:https://www . geesforgeks . org/messagedigest-getinstance-method-in-Java-with-examples/

字符串算法

Java . security . MessageDigest类的 getInstance() 方法，用于返回一个 MessageDigest 类型的对象，该对象应用分配的 MessageDigest 算法。

语法:

public static MessageDigest
  getInstance(String algorithm)
  throws NoSuchAlgorithmException

参数:该方法接受标准算法的名称作为参数。

返回值:该方法提供一个类型为消息摘要的对象。

异常:如果没有提供程序支持特定算法的消息摘要 spi 应用程序，此方法将引发以下异常:

  • no such algorithm 异常:.
  • 空指针异常:如果算法为空。

以下是说明 getInstance() 方法的示例:

例 1:

// Java program to demonstrate
// getInstance() method

import java.security.*;
import java.util.*;

public class GFG1 {
    public static void main(String[] argv)
    {
        try {
            // creating the object of MessageDigest
            // and getting instance
            // By using getInstance() method
            MessageDigest sr
                = MessageDigest.getInstance("MD5");

            // getting the status of MessageDigest object
            String str = sr.toString();

            // printing the status
            System.out.println("Status : " + str);
        }

        catch (NoSuchAlgorithmException e) {

            System.out.println("Exception thrown : " + e);
        }
        catch (NullPointerException e) {

            System.out.println("Exception thrown : " + e);
        }
    }
}

输出:

Status : MD5 Message Digest from SUN, <initialized>

示例 2: 显示 NoSuchAlgorithmException 异常

// Java program to demonstrate
// getInstance() method

import java.security.*;
import java.util.*;

public class GFG1 {
    public static void main(String[] argv)
    {
        try {
            // creating the object of MessageDigest
            // and getting instance
            // By using getInstance() method
            MessageDigest sr
                = MessageDigest.getInstance("GFG");

            // getting the status of MessageDigest object
            String str = sr.toString();

            // printing the status
            System.out.println("Status : " + str);
        }

        catch (NoSuchAlgorithmException e) {

            System.out.println("Exception thrown : " + e);
        }
        catch (NullPointerException e) {

            System.out.println("Exception thrown : " + e);
        }
    }
}

输出:

Exception thrown :
 java.security.NoSuchAlgorithmException:
 GFG MessageDigest not available

getInstance(字符串算法，字符串提供程序)

这个Java . security . MessageDigest类的 getInstance() 方法提供了一个 MessageDigest 类型的对象，该对象应用分配的 MessageDigest 算法和分配的提供程序对象。

语法:

public static MessageDigest 
  getInstance(String algorithm, String provider)
  throws NoSuchAlgorithmException

参数:此方法寻求以下参数作为参数:

  • Algorithm : This is the name of the algorithm to be specified in this instance.
  • Provider : In this example

是指定的提供者的名称

返回值:该方法提供一个类型为消息摘要的对象。

异常:此方法引发以下异常:

  • [Nosuchalogorithm exception: -If a specific provider does not have a message digest Spi implementation of a specific algorithm.
  • 非法理由例外:不合法理由不正当理由不正当理由不正当理由不正当理由不正当理由不正当理由不正当理由不正当理由不正当理由不正当理由不正当理由不正当理由不正当理由不正当理由不正当理由不正当理由不正当理由不正当理由不正当理由不正当理由不正当理由不正当理由不正当理由不正当理由不正当理由不正当理由不正当理由。
  • null pointer exception: If the algorithm is null

以下是说明 getInstance() 方法的示例:

例 1:

// Java program to demonstrate
// getInstance() method

import java.security.*;
import java.util.*;

public class GFG1 {
    public static void main(String[] argv)
    {
        try {
            // creating the object of MessageDigest
            // and getting instance
            // By using getInstance() method
            MessageDigest sr
                = MessageDigest.getInstance(
                    "SHA-384", "SUN");

            // getting the status of MessageDigest object
            String str = sr.toString();

            // printing the status
            System.out.println("Status : " + str);
        }

        catch (NoSuchAlgorithmException e) {

            System.out.println("Exception thrown : " + e);
        }
        catch (NullPointerException e) {

            System.out.println("Exception thrown : " + e);
        }
        catch (NoSuchProviderException e) {

            System.out.println("Exception thrown : " + e);
        }
    }
}

输出:

Status : SHA-384 Message Digest from SUN, <initialized>

示例 2: 显示 NoSuchAlgorithmException 异常

// Java program to demonstrate
// getInstance() method

import java.security.*;
import java.util.*;

public class GFG1 {
    public static void main(String[] argv)
    {
        try {
            // creating the object of MessageDigest
            // and getting instance
            // By using getInstance() method
            MessageDigest sr
                = MessageDigest.getInstance(
                    "GFG", "SUN");

            // getting the status of MessageDigest object
            String str = sr.toString();

            // printing the status
            System.out.println("Status : " + str);
        }

        catch (NoSuchAlgorithmException e) {

            System.out.println("Exception thrown : " + e);
        }
        catch (NullPointerException e) {

            System.out.println("Exception thrown : " + e);
        }
        catch (NoSuchProviderException e) {

            System.out.println("Exception thrown : " + e);
        }
    }
}

输出:

Exception thrown :
 java.security.NoSuchAlgorithmException:
 no such algorithm: GFG for provider SUN

参考:https://docs . Oracle . com/javase/9/docs/API/Java/security/messagedigest . html # getInstance-Java . lang . string-Java . lang . string-

版权属于：月萌API www.moonapi.com，转载请注明出处

本文链接：https://moonapi.com/news/24110.html