Turn KeyPairGeneratorCallback into an Interface.

Applied the same pattern of moving factory methods into a static Util class
as was done in SignatureParameters.Callback

Author: vanitasvitae

pg/src/main/java/org/bouncycastle/openpgp/api/KeyPairGeneratorCallback.java

@@ -7,7 +7,7 @@
 /**
  * Callback to generate a {@link PGPKeyPair} from a {@link PGPKeyPairGenerator} instance.
  */
-public abstract class KeyPairGeneratorCallback
+public interface KeyPairGeneratorCallback
 {
     /**
      * Generate a {@link PGPKeyPair} by calling a factory method on a given generator instance.
@@ -16,45 +16,47 @@ public abstract class KeyPairGeneratorCallback
      * @return generated key pair
      * @throws PGPException
      */
-    public abstract PGPKeyPair generateFrom(PGPKeyPairGenerator generator)
+    PGPKeyPair generateFrom(PGPKeyPairGenerator generator)
         throws PGPException;
 
-    public static KeyPairGeneratorCallback primaryKey()
-    {
-        return new KeyPairGeneratorCallback()
+    static class Util {
+        public static KeyPairGeneratorCallback primaryKey()
         {
-            @Override
-            public PGPKeyPair generateFrom(PGPKeyPairGenerator generator)
-                    throws PGPException
+            return new KeyPairGeneratorCallback()
             {
-                return generator.generatePrimaryKey();
-            }
-        };
-    }
+                @Override
+                public PGPKeyPair generateFrom(PGPKeyPairGenerator generator)
+                    throws PGPException
+                {
+                    return generator.generatePrimaryKey();
+                }
+            };
+        }
 
-    public static KeyPairGeneratorCallback encryptionKey()
-    {
-        return new KeyPairGeneratorCallback()
+        public static KeyPairGeneratorCallback encryptionKey()
         {
-            @Override
-            public PGPKeyPair generateFrom(PGPKeyPairGenerator generator)
-                    throws PGPException
+            return new KeyPairGeneratorCallback()
             {
-                return generator.generateEncryptionSubkey();
-            }
-        };
-    }
+                @Override
+                public PGPKeyPair generateFrom(PGPKeyPairGenerator generator)
+                    throws PGPException
+                {
+                    return generator.generateEncryptionSubkey();
+                }
+            };
+        }
 
-    public static KeyPairGeneratorCallback signingKey()
-    {
-        return new KeyPairGeneratorCallback()
+        public static KeyPairGeneratorCallback signingKey()
         {
-            @Override
-            public PGPKeyPair generateFrom(PGPKeyPairGenerator generator)
-                    throws PGPException
+            return new KeyPairGeneratorCallback()
             {
-                return generator.generateSigningSubkey();
-            }
-        };
+                @Override
+                public PGPKeyPair generateFrom(PGPKeyPairGenerator generator)
+                    throws PGPException
+                {
+                    return generator.generateSigningSubkey();
+                }
+            };
+        }
     }
 }

pg/src/main/java/org/bouncycastle/openpgp/api/OpenPGPKeyEditor.java

@@ -184,7 +184,7 @@ public OpenPGPKeyEditor revokeIdentity(OpenPGPCertificate.OpenPGPIdentityCompone
     public OpenPGPKeyEditor addEncryptionSubkey()
         throws PGPException
     {
-        return addEncryptionSubkey(KeyPairGeneratorCallback.encryptionKey());
+        return addEncryptionSubkey(KeyPairGeneratorCallback.Util.encryptionKey());
     }
 
     public OpenPGPKeyEditor addEncryptionSubkey(KeyPairGeneratorCallback keyGenCallback)
@@ -228,7 +228,7 @@ public void operate(PGPSignatureSubpacketGenerator hashedSubpackets)
     public OpenPGPKeyEditor addSigningSubkey()
         throws PGPException
     {
-        return addSigningSubkey(KeyPairGeneratorCallback.signingKey());
+        return addSigningSubkey(KeyPairGeneratorCallback.Util.signingKey());
     }
 
     public OpenPGPKeyEditor addSigningSubkey(KeyPairGeneratorCallback keyGenCallback)

pg/src/main/java/org/bouncycastle/openpgp/api/OpenPGPKeyGenerator.java

@@ -229,7 +229,7 @@ public WithPrimaryKey signOnlyKey()
         throws PGPException
     {
         return withPrimaryKey(
-            KeyPairGeneratorCallback.primaryKey(),
+            KeyPairGeneratorCallback.Util.primaryKey(),
             SignatureParameters.Callback.Util.modifyHashedSubpackets(new SignatureSubpacketsFunction()
             {
                 @Override
@@ -252,7 +252,7 @@ public PGPSignatureSubpacketGenerator apply(PGPSignatureSubpacketGenerator subpa
     public WithPrimaryKey withPrimaryKey()
         throws PGPException
     {
-        return withPrimaryKey(KeyPairGeneratorCallback.primaryKey());
+        return withPrimaryKey(KeyPairGeneratorCallback.Util.primaryKey());
     }
 
     /**
@@ -408,7 +408,7 @@ public WithPrimaryKey addUserId(
         public WithPrimaryKey addEncryptionSubkey()
             throws PGPException
         {
-            return addEncryptionSubkey(KeyPairGeneratorCallback.encryptionKey());
+            return addEncryptionSubkey(KeyPairGeneratorCallback.Util.encryptionKey());
         }
 
         /**
@@ -500,7 +500,7 @@ public void operate(PGPSignatureSubpacketGenerator hashedSubpackets)
         public WithPrimaryKey addSigningSubkey()
             throws PGPException
         {
-            return addSigningSubkey(KeyPairGeneratorCallback.signingKey());
+            return addSigningSubkey(KeyPairGeneratorCallback.Util.signingKey());
         }
 
         /**