Java中的 MessageDigest getDigestLength() 方法及示例

MessageDigest类的getDigestLength()方法用于获取消息摘要对象的对象大小（以字节为单位）。

句法：

public final int getDigestLength()

返回值：此方法以字节形式提供消息摘要的长度。

以下是说明getDigestLength()方法的示例：

示例 1：

// Java program to demonstrate
// getDigestLength() method
  
import java.security.*;
import java.util.*;
  
public class GFG1 {
    public static void main(String[] argv)
    {
        try {
  
            // creating object of MessageDigest
            MessageDigest msd
                = MessageDigest.getInstance("SHA-256", "SUN");
  
            // getting the length of MessageDigest of object msd
            // by using method getDigestLength()
            int length = msd.getDigestLength();
  
            // printing the provider name
            System.out.println("Message digest length : "
                               + length);
        }
  
        catch (NoSuchAlgorithmException e) {
  
            System.out.println("Exception thrown : " + e);
        }
        catch (NoSuchProviderException e) {
  
            System.out.println("Exception thrown : " + e);
        }
    }
}

输出：

Message digest length : 32

示例 2：

// Java program to demonstrate
// getDigestLength() method
  
import java.security.*;
import java.util.*;
  
public class GFG1 {
    public static void main(String[] argv)
    {
        try {
  
            // creating object of MessageDigest
            MessageDigest msd
                = MessageDigest.getInstance("MD5");
  
            // getting the length of MessageDigest of object msd
            // by using method getDigestLength()
            int length = msd.getDigestLength();
  
            // printing the provider name
            System.out.println("Message digest length : "
                               + length);
        }
  
        catch (NoSuchAlgorithmException e) {
  
            System.out.println("Exception thrown : " + e);
        }
    }
}

输出：

Message digest length : 16

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