recovered text size should be equal to the size of cipher text. AES cipher can not distiguish the ENCRYPT mode and DECRYPT mode, doFinal method normally need more unnecessary recoveredText size in decryption case. The following program demonstrates this.

import java.io.PrintStream;
import java.security.*;
import java.security.spec.*;
import java.util.Random;

import javax.crypto.*;
import javax.crypto.spec.*;
import java.security.Provider;
import com.sun.advcrypto.provider.SunAES;

public class test {

     public static void main( String argv[] ) {
    
     byte[] ip=new byte[0];
     String algorithm = "AES";
     String mode = "CBC";
    byte[] iv = null;
    String padding = "PKCS5Padding";
     int keyStrength=128;
     AlgorithmParameterSpec aps = null;
    
     try{
    
     // Initialization
Random rdm = new Random();
byte[] plainText=new byte[125];
rdm.nextBytes(plainText);
System.out.println("plain text length is "+plainText.length);
        
  Cipher ci = Cipher.getInstance( algorithm + "/" + mode + "/" + padding);
     KeyGenerator kg = KeyGenerator.getInstance( algorithm);
     kg.init(keyStrength);
     SecretKey key = kg.generateKey();

                // encrypt
     ci.init( Cipher.ENCRYPT_MODE, key, aps);
     byte[] cipherText = new byte[ci.getOutputSize(plainText.length)];
System.out.println("cipherText length is "+cipherText.length);
     int offset = ci.update(plainText, 0, plainText.length, cipherText, 0);
     ci.doFinal( cipherText, offset );
  
if (!mode.equalsIgnoreCase("ECB")) {
iv = ci.getIV();
aps = new IvParameterSpec(iv);
} else aps = null;


//Decrypt
ci.init( Cipher.DECRYPT_MODE, key, aps);
  byte[] recoveredText = new byte[125];
System.out.println("Recovertext length is "+recoveredText.length);
     int len = ci.doFinal( cipherText, 0, cipherText.length, recoveredText );

     }catch(Exception ex){
     System.out.println("FAILED");
     ex.printStackTrace();
    
     }
     }
}

lwang:/home/lw129730/AES/testcode/test( 159 )%java test
plain text length is 125
cipherText length is 128
Recovertext length is 125
FAILED
javax.crypto.ShortBufferException: The output buffer is too short
        at cryptix.jce.provider.cipher.SunAES_h.b(DashoA6275)
        at cryptix.jce.provider.cipher.BlockCipher.engineDoFinal(DashoA6275)
        at javax.crypto.Cipher.doFinal(DashoA6275)
        at test.main(test.java:90)