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Java Forum / General / February 2008showing memory used by a Java app in the app itself
Hi, some Java applications display the memory used by the application itself. This is the case, for example, in the IntelliJ IDEA IDE (best Java app ever written in my opinion if I had to choose one but that's another topic). And surely enough if you change the heap settings by (-Xmx et al. JVM parameters) this correctly reflect in IntelliJ (e.g. it shows "100 M out of 256 M" used). Note that I know how to use a profiler (I'm using JProfiler) as well as how to obtain information about the memory used from the OS point and view but this is not the topic of my post: my question is not about how/where to find memory leaks or how to use the OS to see how much memory is used. I really want to know how a Java program can obtain memory usage information about itself. Do I have to go into tricky reference counting and approximating the size of all objects or are there any convenient methods to call ? I've tried to search the group's archive but didn't find much (my Google-fu may not be very strong), Alex On Feb 7, 7:29 am, alexandre_pater...@yahoo.fr wrote: ... > This is the case, for example, in the IntelliJ IDEA IDE > (best Java app ever written in my opinion if I had to > choose one but that's another topic). Responding to myself: This is also the case for Eclipse, for example the plugin called 'freemem' does exactly that too. I'm not looking after how much memory is used by the OS but about how much heap space (and what the max heap space is) is currently used (and want to update that regularly), in summary just like IntelliJ IDEA does and just like 'freemem' does for Eclipse. This is for a Java 1.6 application. > I really want to know how a Java program can obtain > memory usage information about itself. java.lang.Runtime.freeMemory(); java.lang.Runtime.totalMemory(); <http://java.sun.com/javase/6/docs/api/java/lang/Runtime.html> > alexandre_pater...@yahoo.fr wrote: > > I really want to know how a Java program can obtain > > memory usage information about itself. > > java.lang.Runtime.freeMemory(); > java.lang.Runtime.totalMemory(); They're not static methods apparently but... Excellent :) My Google-fu certainly ain't very strong :) Thank you for the quick answer, Alex >> alexandre_pater...@yahoo.fr wrote: >>> I really want to know how a Java program can obtain [quoted text clipped - 3 lines] > > They're not static methods apparently but... Why does that matter? Do you need static methods? Would referencing the Runtime instance cause you trouble?  SignatureLew >>> alexandre_pater...@yahoo.fr wrote: >>>> I really want to know how a Java program can obtain [quoted text clipped - 6 lines] > Why does that matter? Do you need static methods? Would referencing > the Runtime instance cause you trouble? If you don't know how to get the runtime, it might :-) Without bothering to google it, I think it is easy System.getRuntime() or Runtime.getRuntime(). Google will answer you. SignatureDaniel Pitts' Tech Blog: <http://virtualinfinity.net/wordpress/> >>>> alexandre_pater...@yahoo.fr wrote: >>>>> I really want to know how a Java program can obtain [quoted text clipped - 11 lines] > Without bothering to google it, I think it is easy System.getRuntime() > or Runtime.getRuntime(). Google will answer you. Actually, I found the Javadocs to be a virtually instantaneous source of the relevant information. I still want to know why the fact that the methods aren't static is a problem. Why is that? SignatureLew >>>>> alexandre_pater...@yahoo.fr wrote: >>>>>> I really want to know how a Java program can obtain [quoted text clipped - 17 lines] > I still want to know why the fact that the methods aren't static is a > problem. Why is that? Entry points are sometimes hard to find. You can't just use "new Runtime().freeMemory();", you have to find the correct runtime instance. Reading the docs will indeed imbue one with that information, but that wasn't the point I was making. SignatureDaniel Pitts' Tech Blog: <http://virtualinfinity.net/wordpress/> >>>>>> alexandre_pater...@yahoo.fr wrote: >>>>>>> I really want to know how a Java program can obtain [quoted text clipped - 22 lines] > instance. Reading the docs will indeed imbue one with that information, > but that wasn't the point I was making. But why are static methods a requirement for the OP? SignatureLew >>>>>>> alexandre_pater...@yahoo.fr wrote: >>>>>>>> I really want to know how a Java program can obtain [quoted text clipped - 24 lines] > > But why are static methods a requirement for the OP? Perhaps the OP's "They're not static methods apparently" was merely a passing remark to the effect that Mark's "java.lang.Runtime.freeMemory();" had the superficial appearance of a static method whereas it is really an instance method. Perhaps if Mark had written "Runtime.getRuntime().freeMemory()" the OP wouldn't have commented? I must admit I often use the Classname.methodname() shorthand to refer to instance methods, so I'm not criticizing Mark, just hypothesising about the OP's remark. > Perhaps the OP's "They're not static methods apparently" was merely a > passing remark to the effect that Mark's [quoted text clipped - 5 lines] > Classname.methodname() shorthand to refer to instance methods, so I'm > not criticizing Mark, just hypothesising about the OP's remark. I usually use a number sign (#) prefix to denote instance members and a dot prefix to denote class members. IIRC, I picked up that habit from the Javadoc engine, which would interpret this notation that way. Wouldn't this be a viable alternative? Lew wrote: >>>> I still want to know why the fact that the methods aren't static is >>>> a problem. Why is that? > Perhaps the OP's "They're not static methods apparently" was merely a > passing remark to the effect that Mark's [quoted text clipped - 5 lines] > Classname.methodname() shorthand to refer to instance methods, so I'm > not criticizing Mark, just hypothesising about the OP's remark. Mark shouldn't be criticized - referring to the method from the class, as I pointed out upthread, is a standard way to communicate about the Javadocs. Since instances are meaningless in the context of documentation, it would be improper to infer that a static method is intended. 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