Determine whether .class file was compiled with debug info?

Question

How can I determine for any Java .class file if that was compiled with debug info or not?

How can I tell exactly what -g{source|lines|vars} option was used?

Answer 1

If you're on the command line, then javap -l will display LineNumberTable and LocalVariableTable if present:

peregrino:$ javac -d bin -g:none src/Relation.java  peregrino:$ javap -classpath bin -l Relation  public class Relation extends java.lang.Object{ public Relation();  peregrino:$ javac -d bin -g:lines src/Relation.java  peregrino:$ javap -classpath bin -l Relation  public class Relation extends java.lang.Object{ public Relation();   LineNumberTable:     line 1: 0    line 33: 4  peregrino:$ javac -d bin -g:vars src/Relation.java  peregrino:$ javap -classpath bin -l Relation  public class Relation extends java.lang.Object{ public Relation();    LocalVariableTable:     Start  Length  Slot  Name   Signature    0      5      0    this       LRelation; 

javap -c will display the source file if present at the start of the decompilation:

peregrino:$ javac -d bin -g:none src/Relation.java  peregrino:$ javap -classpath bin -l -c Relation | head public class Relation extends java.lang.Object{   ...  peregrino:$ javac -d bin -g:source src/Relation.java  peregrino:$ javap -classpath bin -l -c Relation | head Compiled from "Relation.java" public class Relation extends java.lang.Object{   ... 

Programmatically, I'd look at ASM rather than writing yet another bytecode reader.