Is there asm nop equivalent in java?

Question

When I program C/C++ with Visual Studio I often use __asm nop; command to insert a noop code in order to have something to break on. For instance:

if (someCondition()) {   __asm nop; } 

I have no idea what to do when the condition occurs, but I want to stop the execution and examine the current state. Sometimes someCondition() is simple enough to create a conditional breakpoint, but conditional breakpoints slow down the execution significantly, besides it is not always possible.

Now, in C# I break into the debugger directly either by calling System.Diagnostics.Debugger.Break() or System.Diagnostics.Debugger.Launch().

Now I am forced to program Java and until now I have found no better alternative than just do System.out.println("bla-bla") and set a breakpoint there. Again, please consider the case when a conditional breakpoint is not feasible.

So, I wonder - is there an __asm nop or System.Diagnostics.Debugger.Break() alternative in Java?

Answer 1

In bytecode you have a nop instruction, but there's no nop statement in the Java language.

You can add an extra ; on a line by itself and the code will still compile, but that's not much more meaningful than adding an empty line.

Another "does nothing" statement could be:

assert true; 

which has no side-effects what so ever, and can be turned off when executing the program.

As it turns out, assert true does not seem to generate any bytecode instructions, which causes break-points on assert true to be skipped all together. Eclipse is however able to break on a statement such as

assert Boolean.TRUE; 

which is quite similar.

Answer 2

Java interprets this as an empty statement:

; 

Though, as noted in comments, Eclipse won't let you set a breakpoint here. If you want something useless that you can put a breakpoint on that's also nice and easy to type, I suggest:

if(false){} 

Your compiler might warn you that this is never entered, which can be useful for reminding you to take it out before compiling for production. Hope this helps!