how do we know which method (java.class) has called the current one

Question

Example: If I have two classes: A and B. both class can call a method in C (example: the init() method)

From C, how do we know where the call is from (from Class A or Class B) ?

You can look at the stack trace but this is rarely a good idea (and its relatively slow) You should instead pass to C all the important information. BTW You can pass a class as an argument e.g. `init(A.class);` — Peter Lawrey, Oct 11 '12 at 07:58
Technically it might be interesting, but in general code should not depend on the caller, it should depend on its parameters — stefan bachert, Oct 11 '12 at 08:03
See also http://stackoverflow.com/questions/3178249/how-can-i-know-which-method-call-my-method?rq=1 — DNA, Oct 31 '12 at 11:25
possible duplicate of [In Java, how do I find the caller of a method using stacktrace or reflection?](http://stackoverflow.com/questions/421280/in-java-how-do-i-find-the-caller-of-a-method-using-stacktrace-or-reflection) — DNA, Oct 31 '12 at 11:28

score 3 · Accepted Answer · edited May 23 '17 at 11:56

To do it right, you should provide C's method with that information, for example via an enum or class parameter:

public void init(Object otherArg, Class<?> caller) {
    ...
}

or

public void init(Object otherArg, CallerEnum caller) {
    ...
}

But if you don't care, there is another way using the stack trace. Have a look at Get current stack trace in Java and use the second StackTraceElement from the top of the stack to get the method that called the current one.

score 3 · Answer 2 · answered Oct 11 '12 at 08:13

This may be useful:

StackTraceElement[] stackTraceElements = Thread.currentThread().getStackTrace();

you can use this to get the stack trace of the current thread in a StackTraceElement array where the first element of the array is the most recent method invocation sequence on the stack
provided the returned array is of non-zero length. StackTraceElement has methods like getClassName, getMethodName, etc., which one can use to find the caller class name or method name.

urir · Answer 3 · 2012-10-11T08:05:50.737

1

Taken from somewhere of the web...

private static final int CLIENT_CODE_STACK_INDEX;

static {
    // Finds out the index of "this code" in the returned stack trace - funny but it differs in JDK 1.5 and 1.6
    int i = 0;
    for (StackTraceElement ste : Thread.currentThread().getStackTrace()) {
        i++;
        if (ste.getClassName().equals(MyClass.class.getName())) {
            break;
        }
    }
    CLIENT_CODE_STACK_INDEX = i;
}

public static String getCurrentMethodName() {
    return Thread.currentThread().getStackTrace()[CLIENT_CODE_STACK_INDEX].getMethodName();
}
public static String getCallerMethodName() {
    return Thread.currentThread().getStackTrace()[CLIENT_CODE_STACK_INDEX+1].getMethodName();
}

edited Oct 11 '12 at 08:05

answered Oct 11 '12 at 07:59

urir

1,960
3
23
40

1

I suspect the different depth depends on the number of call levels inside the getStackTrace which is called before the snapshot is taken. It could differ between vendors as well. – Peter Lawrey Oct 11 '12 at 08:02
Executed on class X.foo - will return "foo", the static block is to prevent the problem you referred. – urir Oct 11 '12 at 08:06
1

I was trying to explain why the static block was needed as you had the comment `funny but it differs in JDK 1.5 and 1.6` – Peter Lawrey Oct 11 '12 at 08:08

score 0 · Answer 4 · answered Nov 05 '12 at 12:47

0

I found an easier solution (for me :D )

public <T> void init(Class<T> clazz) {
     if (!clazz.getSimpleName().equals("MyClassName")) {
          // do something
     }else{
          // do something
     }
}

answered Nov 05 '12 at 12:47

Karim Oukara

2,638
8
38
51

how do we know which method (java.class) has called the current one

4 Answers4