Recompiling Java code for AR BPA invoice print fails

I used a Java decompiler to extract Java code from class files for AR BPA print program. The class file name is PrintInvoiceThread.java and I got the file from $JAVA_TOP/oracle/apps/ar/bpa/presentment/cp in middle-tier. I copied the Java source code (PrintInvoiceThread.java) back to $JAVA_TOP/oracle/apps/ar/bpa/presentment/cp in middle-tier. I used the following command to recompile the code in Linux:

javac PrintInvoiceThread.java

But I get the following error message:

PrintInvoiceThread.java:149: cannot find symbol

symbol : variable localObject1

location: class oracle.apps.ar.bpa.presentment.cp.PrintInvoiceThread

/* 173 */ localObject1 = this.paramList.nextParameter();