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  • Java, user input to the command line when using Runtime.getRuntime().exec(command);

    - by user1557354
    I dont think this is possible, but I have been using: Process p = Runtime.getRuntime().exec(command); to run commands on the command line, but now I have come accross a situation where the command I am running part way through will ask for some user input, for example a username. This can not be resolved by a argument to the command that is being exec, is there any way I can pass the username to the same command line instance and continue? Thanks in advance.

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  • Java: I've created a list of word objects to include the name and the frequency, but having trouble

    - by adam08
    Hi Everyone, I'm working on a project which has a dictionary of words and I'm extracting them and adding them to an ArrayList as word objects. I have a class called Word as below. What I'm wondering is how do I access these word objects to update the frequency? As part of this project, I need to only have one unique word, and increase the frequency of that word by the number of occurrences in the dictionary. Word(String word) { this.word = word; this.freq = 0; } public String getWord() { return word; } public int getFreq() { return freq; } public void setFreq() { freq = freq + 1; } This is how I am adding the word objects to the ArrayList...I think it's ok? String pattern = "[^a-zA-Z\\s]"; String strippedString = line.replaceAll(pattern, ""); line = strippedString.toLowerCase(); StringTokenizer st = new StringTokenizer(line); while (st.hasMoreTokens()) { String newWord = st.nextToken(); word.add(new Word(newWord)); count++; }

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  • In Java, can a final field be initialized from a constructor helper?

    - by csj
    I have a final non-static member: private final HashMap<String,String> myMap; I would like to initialize it using a method called by the constructor. Since myMap is final, my "helper" method is unable to initialize it directly. Of course I have options: I could implement the myMap initialization code directly in the constructor. MyConstructor (String someThingNecessary) { myMap = new HashMap<String,String>(); myMap.put("blah","blahblah"); // etc... // other initialization stuff unrelated to myMap } I could have my helper method build the HashMap, return it to the constructor, and have the constructor then assign the object to myMap. MyConstructor (String someThingNecessary) { myMap = InitializeMyMap(someThingNecessary); // other initialization stuff unrelated to myMap } private HashMap<String,String> InitializeMyMap(String someThingNecessary) { HashMap<String,String> initializedMap = new HashMap<String,String>(); initializedMap.put("blah","blahblah"); // etc... return initializedMap; } Method #2 is fine, however, I'm wondering if there's some way I could allow the helper method to directly manipulate myMap. Perhaps a modifier that indicates it can only be called by the constructor? MyConstructor (String someThingNecessary) { InitializeMyMap(someThingNecessary); // other initialization stuff unrelated to myMap } // helper doesn't work since it can't modify a final member private void InitializeMyMap(String someThingNecessary) { myMap = new HashMap<String,String>(); myMap.put("blah","blahblah"); // etc... }

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  • Which of the following Java coding fragments is better?

    - by Simon
    This isn't meant to be subjective, I am looking for reasons based on resource utilisation, compiler performance, GC performance etc. rather than elegance. Oh, and the position of brackets doesn't count, so no stylistic comments please. Take the following loop; Integer total = new Integer(0); Integer i; for (String str : string_list) { i = Integer.parse(str); total += i; } versus... Integer total = 0; for (String str : string_list) { Integer i = Integer.parse(str); total += i; } In the first one i is function scoped whereas in the second it is scoped in the loop. I have always thought (believed) that the first one would be more efficient because it just references an existing variable already allocated on the stack, whereas the second one would be pushing and popping i each iteration of the loop. There are quite a lot of other cases where I tend to scope variables more broadly than perhaps necessary so I thought I would ask here to clear up a gap in my knowledge. Also notice that assignment of the variable on initialisation either involving the new operator or not. Do any of these sorts of semi-stylistic semi-optimisations make any difference at all?

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  • Is it possible to use inheritance in this situation? (Java)

    - by they changed my name
    I have ClassA and ClassB, with ClassA being the superclass. ClassA uses NodeA, ClassB uses NodeB. First problem: method parameters. ClassB needs NodeB types, but I can't cast from the subclass to the superclass. That means I can't set properties which are unique to NodeB's. Second problem: When I need to add nodes toClassB, I have to instantiate a new NodeB. But, I can't do this in the superclass, so I'd have to rewrite the insertion to use NodeB. Is there a way around it or am I gonna have to rewrite the whole thing?

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  • Java: Superclass to construct a subclass on certain conditions, possible?

    - by ramihope
    I have this condition public class A { public action() { System.out.println("Action done in A"); } } public class B extends A { public action() { System.out.println("Action done in B"); } } when I create an instance of B, the action will do just actions in B, as it overrides the action of the superclass. the problem is that in my project, the super class A is already used too many times, and I am looking for a way that under certain conditions, when i create an instance of A it makes a check and if it is true, replace itself with B. public class A { public A() { if ([condition]) { this = new B(); } } public action() { System.out.println("Action done in A"); } } A a = new A(); a.action(); // expect to see "Action done in B"... is this possible in some way?

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  • How to queue and call actual methods (rather than immediately eval) in java?

    - by alleywayjack
    There are a list of tasks that are time sensitive (but "time" in this case is arbitrary to what another program tells me - it's more like "ticks" rather than time). However, I do NOT want said methods to evaluate immediately. I want one to execute after the other finished. I'm using a linked list for my queue, but I'm not really sure how/if I can access the actual methods in a class without evaluating them immediate. The code would look something like... LinkedList<Method> l = new LinkedList<Method>(); l.add( this.move(4) ); l.add( this.read() ); l.removeFirst().call(); //wait 80 ticks l.removeFirst().call(); move(4) would execute immediately, then 80 ticks later, I would remove it from the list and call this.read() which would then be executed. I'm assuming this has to do with the reflection classes, and I've poked around a bit, but I can't seem to get anything to work, or do what I want. If only I could use pointers...

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  • Extracting two strings from quotations in Java using regex?

    - by user656710
    Hi everyone, I'm new to using patterns and looked everywhere on the internet for an explanation to this problem. Say I have a string: String info = "Data I need to extract is 'here' and 'also here'"; How would I extract the words: here also here without the single quotes using a pattern? This is what I have so far... Pattern p = Pattern.compile("(?<=\').*(?=\')"); But it returns ( here and 'also here ) minus the brackets, that is just for viewing. It skips over the second piece of data and goes straight to the last quote... Thank you!

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  • Is it possible to write a generic +1 method for numeric box types in Java?

    - by polygenelubricants
    This is NOT homework. Part 1 Is it possible to write a generic method, something like this: <T extends Number> T plusOne(T num) { return num + 1; // DOESN'T COMPILE! How to fix??? } Short of using a bunch of instanceof and casts, is this possible? Part 2 The following 3 methods compile: Integer plusOne(Integer num) { return num + 1; } Double plusOne(Double num) { return num + 1; } Long plusOne(Long num) { return num + 1; } Is it possible to write a generic version that bound T to only Integer, Double, or Long?

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  • How to pass a file (read from Java) most effectively to a native method?

    - by soc
    Hi, I have approx. 30000 files (1MB each) which I want to put into a native method, which requires just an byte array and the size of it as arguments. I looked through some examples and benchmarks (like http://nadeausoftware.com/articles/2008/02/java_tip_how_read_files_quickly) but all of them do some other fancy things. Basically I don't care about the contents of the file, I don't want to access something in that file or the byte array or do anything else with it. I just want to put a file into a native method which accepts an byte array as fast as possible. At the moment I'm using RandomAccessFile, but that's horribly slow (10MB/s). Is there anything like byte[] readTheWholeFile(File file){ ... } which I could put into native void fancyCMethod(readTheWholeFile(myFile), myFile.length()) What would you suggest?

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  • How can I tell what is using the memory when there is a heap overflow in Java?

    - by Grae
    Hi all, I know a little about profiling, but what I am particularlly insterest in, is what has all the memory when I get these heap over flow exceptions. I will start getting them after about a hour of debugging. I am hoping there is some sort of dump or something, that I can use to get a list of what instances are around at the time the program starts. By the way, sorry if this is a lazy question. I really shoud put sometime in learning about profiling. Grae

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  • How can I get relative path of the folders in my project? (java)

    - by masterkapu
    How can I get the relative path of the folders in my project (using code)? I created new folder in my project and I want its relative path so no matter where is the app the path will be correct. Maybe this can be useful: I trying to do it not inside any function just inside the class and I want to init with it a final variable. the app is android and the class is "extends Activity" thanks

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