Java equivalent to python “dir”?

Question

Is there an equivalent to \"dir\" in python for java, or a library which provides similar functionality (i.e. properties of objects and classes output as informative strings

Answer 1

I was thinking if using javap would be a good choice. The man says javap - The Java Class File Disassembler

and I could see the built in methods by

javap java.lang.Double | grep -i int
public static final int MAX_EXPONENT;
public static final int MIN_EXPONENT;
public static final int SIZE;
public int intValue();
public int hashCode();
public int compareTo(java.lang.Double);
public static int compare(double, double);
public int compareTo(java.lang.Object);

Taking System.out.println(),

javap -c java.lang.System | grep -i out
public static final java.io.PrintStream out;
public static void setOut(java.io.PrintStream);
   4: invokestatic  #4                  // Method setOut0:(Ljava/io/PrintStream;)V
   8: putstatic     #98                 // Field out:Ljava/io/PrintStream;

and then do javap java.io.PrintStream

Answer 2

There's nothing in the standard library that accomplishes exactly what dir() does, but you can get the same information using java.lang.reflect. Specifically, investigating and discovering members of a class is explained in the documentation on discovering class members. Using that API you can easily find out what you need to know about the attributes of a class.

In fact, implementing dir() yourself would just be a matter of defining a method that introspects the methods and fields of a class and either assembles a collection of the info or prints whatever information you'd like to know.

dir() has limited usefulness in Java because Java is not interactive, but if you need it for educational/investigative purposes or for application logic, the reflection API is always there.