FULL PRODUCT VERSION :
java -version
java version "1.7.0_03"
Java(TM) SE Runtime Environment (build 1.7.0_03-b04)
Java HotSpot(TM) 64-Bit Server VM (build 22.1-b02, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Linux serverName 3.10.17 #1 SMP Tue Oct 29 10:41:00 CDT 2013 x86_64 x86_64 x86_64 GNU/Linux

A DESCRIPTION OF THE PROBLEM :
Refer to bug report JDK-2017913 and JDK-4092480. Both of which are marked as fixed as of 1998.

The bug is not fixed.
    


STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
    dfFoo = new DecimalFormat("0000;-000");
    System.out.println(dfFoo.format(42));
    System.out.println(dfFoo.format(-42));
    System.out.println();

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
 0042
 -042
ACTUAL -
 0042
 -0042

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.text.*;

public class TestApp extends java.lang.Object
{
  public static void main(java.lang.String[] args)
  {
    DecimalFormat dfFoo;
    
    dfFoo = new DecimalFormat("0000;-000");
    System.out.println(dfFoo.toPattern());
    System.out.println(dfFoo.format(42));
    System.out.println(dfFoo.format(-42));
    System.out.println();
    
    dfFoo.applyPattern("000;-000");
    System.out.println(dfFoo.toPattern());
    System.out.println(dfFoo.format(42));
    System.out.println(dfFoo.format(-42));
    System.out.println();
    
    dfFoo.applyPattern("000;-0000");
    System.out.println(dfFoo.toPattern());
    System.out.println(dfFoo.format(42));
    System.out.println(dfFoo.format(-42));
    System.out.println();
    
    dfFoo.applyPattern("0000;-000");
    System.out.println(dfFoo.toPattern());
    System.out.println(dfFoo.format(42));
    System.out.println(dfFoo.format(-42));
    System.out.println();
    
    
  }
    
}
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Define patterns for positive and negative.

    DecimalFormat dfPos = new DecimalFormat("0000");
    DecimalFormat dfNeg = new DecimalFormat("000");
    System.out.println(dfPos.format(42));
    System.out.println(dfNeg.format(-42));


This produces the expected values.
0042
-042