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  • Executing in java code an external program that takes arguments

    - by rmaster
    Process p; String line; String path; String[] params = new String [3]; params[0] = "D:\\prog.exe"; params[1] = picA+".jpg"; params[2] = picB+".jpg"; try { p = Runtime.getRuntime().exec(params); BufferedReader input = new BufferedReader (new InputStreamReader(p.getInputStream())); while ((line = input.readLine()) != null) System.out.println(line); input.close(); } catch (IOException e) {System.out.println(" procccess not read"+e);} i don't get any error, just nothing in cmd.exe prog.exe is working fine What to improve in order to make this code working?

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  • Passing a class ("Country.class") as an argument in Java

    - by Coronatus
    I'm trying to make a method that takes an argument of Country.class, User.class etc, and returns argument.count(). All the possible classes that I would give to this method extend from Model and have the method count(). My code: private static long <T> countModel(Model<T> clazz) { return clazz.count(); } Called by: renderArgs.put("countryCount", countModel(Country.class)); However this just doesn't work at all. How do I do this, please?

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  • Container of Generic Types in java

    - by Cyker
    I have a generic class Foo<T> and parameterized types Foo<String> and Foo<Integer>. Now I want to put different parameterized types into a single ArrayList. What is the correct way of doing this? Candidate 1: public class MMM { public static void main(String[] args) { Foo<String> fooString = new Foo<String>(); Foo<Integer> fooInteger = new Foo<Integer>(); ArrayList<Foo<?> > list = new ArrayList<Foo<?> >(); list.add(fooString); list.add(fooInteger); for (Foo<?> foo : list) { // Do something on foo. } } } class Foo<T> {} Candidate 2: public class MMM { public static void main(String[] args) { Foo<String> fooString = new Foo<String>(); Foo<Integer> fooInteger = new Foo<Integer>(); ArrayList<Foo> list = new ArrayList<Foo>(); list.add(fooString); list.add(fooInteger); for (Foo foo : list) { // Do something on foo. } } } class Foo<T> {} In a word, it is related to the difference between Foo<?> and the raw type Foo. Update: Grep What is the difference between the unbounded wildcard parameterized type and the raw type? on this link may be helpful.

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  • Java iterative vs recursive

    - by user1389813
    Can anyone explain why the following recursive method is faster than the iterative one (Both are doing it string concatenation) ? Isn't the iterative approach suppose to beat up the recursive one ? plus each recursive call adds a new layer on top of the stack which can be very space inefficient. private static void string_concat(StringBuilder sb, int count){ if(count >= 9999) return; string_concat(sb.append(count), count+1); } public static void main(String [] arg){ long s = System.currentTimeMillis(); StringBuilder sb = new StringBuilder(); for(int i = 0; i < 9999; i++){ sb.append(i); } System.out.println(System.currentTimeMillis()-s); s = System.currentTimeMillis(); string_concat(new StringBuilder(),0); System.out.println(System.currentTimeMillis()-s); } I ran the program multiple time, and the recursive one always ends up 3-4 times faster than the iterative one. What could be the main reason there that is causing the iterative one slower ?

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  • Simple Java math operations

    - by user1730056
    I'm making a BMI calculator that doesn't seem to be working. The math operations work if i just do something like w/h, but once i had the brackets, it returns an error. If i change the variables w and h and use a constant number, the operation works. Another problem is that although i'm making result a double, it seems to be rounding to the nearest int. Could someone tell me what I'm doing wrong here? public class ass10 { public static void main(String[] args) { bmi(223,100); } public static bmi(int w, int h){ double result; result = (w/(h*h))*703 System.out.println(result) } }

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  • Splitting up input using regular expressions in Java

    - by Joe24
    I am making a program that lets a user input a chemical for example C9H11N02. When they enter that I want to split it up into pieces so I can have it like C9, H11, N, 02. When I have it like this I want to make changes to it so I can make it C10H12N203 and then put it back together. This is what I have done so far. using the regular expression I have used I can extract the integer value, but how would I go about get C10, H11 etc..? System.out.println("Enter Data"); Scanner k = new Scanner( System.in ); String input = k.nextLine(); String reg = "\\s\\s\\s"; String [] data; data = input.split( reg ); int m = Integer.parseInt( data[0] ); int n = Integer.parseInt( data[1] );

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  • Problems reading text file data in Java

    - by user1828401
    I have this code: BufferedReader br =new BufferedReader(new FileReader("userdetails.txt")); String str; ArrayList<String> stringList = new ArrayList<String>(); while ((str=br.readLine())!=null){ String datavalue [] = str.split(","); String category = datavalue[0]; String value = datavalue[1]; stringList.add(category); stringList.add(value); } br.close(); it works when the variables category and value do not have a comma(,),however the values in the variable value does contain commas.Is there a way that I can split the index of the without using comma?

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  • Help making a button open another app with Java/Android

    - by user569503
    I am trying to learn to make a simple app that opens a couple of other apps to eliminate the need for another apps. I just can't figure it out. From reading here and other places it seems this should work. Button batteryhistory = (Button)findViewById(R.string.BatteryHistoryButtonDialog); batteryhistory.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View view) { Intent i = new Intent(); ComponentName n = new ComponentName("com.android.settings", "com.android.settings.BatteryHistory"); i.setComponent(n); startActivity(i); Thanks so much for the help :D

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  • pls give reason why this java program always comes to the else part

    - by Anbu
    public class Test { public static void main(String[] args){ if (5.0 5) // (5.0<5) for both case it is going to else System.out.println("5.0 is greater than 5"); else System.out.println("else part always comes here"); /another sample/ if (5.0 == 5) System.out.println("equals"); else System.out.println("not equal"); } } can any one explain the first "if statement" why it always come to else part

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  • Returning string in java using 3 parameters

    - by user2905118
    Need to write a method describePerson() that takes 3 parameters, a String giving a person’s name, a boolean indicating their gender (true for female, false for male), and an integer giving their age. The method should return a String formatted as in the following examples: Lark is female. She is 2 years old. Or Jay is male. He is 1 year old. I am not sure how to write it correctly (my code): int describePerson(String name, boolean gender, int age) { String words=""; if(gender==true) return (name + "is "+gender+". "+"She is"+age+ "years old.); else return (name + "is "+gender+". "+"She is"+age+ "years old.); } The outcome "year" and "years" is also differs, but i don't know how to make it correct..

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  • formatting and converting in java

    - by mike_hornbeck
    I have few small basic problems : How to format : int i = 456; to give output : ""00000456" ? I've tried %08d but it's not working. Next thing is a problem with conversion and then formatting. I have side and height of triangle, let's say int's 4,7, and 7 is the height. From formula for field we know that F=1/2(a*h). So how to get F as float, with precision up to 10 places ? float f = a*h; works fine, but multiplying it by 0.5 gives error and by 1/2 returns 0.

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  • Pass off execution to different/specific thread in Java

    - by Mike
    I have about 4 threads. One thread keeps checking some data that the other thread is updating. The others are doing some processing in the background. All have been started at this point. My question is when the checking thread sees that the data has not been updated yet I currently sleep for a little bit but is there any way for me to tell the system to back to executing the thread that does the updating? That or is there any way I can put something like a listener on the data(a String) and once its updated an event will fire that will do what it needs to do? I tried using yield() and it seemed to just keep returning to the thread I called yield() from. Thanks

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  • singleton pattern in java- lazy Intialization

    - by flash
    public static MySingleton getInstance() { if (_instance==null) { synchronized (MySingleton.class) { _instance = new MySingleton(); } } return _instance; } 1.is there a flaw with the above implementation of the getInstance method? 2.What is the difference between the two implementations.? public static synchronized MySingleton getInstance() { if (_instance==null) { _instance = new MySingleton(); } return _instance; } I have seen a lot of answers on the singleton pattern in stackoverflow but the question I have posted is to know mainly difference of 'synchronize' at method and block level in this particular case.

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  • Searching in a TreeMap (Java)

    - by Kronen
    I need to do a search in a map of maps and return the keys this element belong. I think this implementation is very slow, can you help me to optimize it?. I need to use TreeSet and I can't use contains because they use compareTo, and equals/compareTo pair are implemented in an incompatible way and I can't change that. (sorry my bad english) Map m = new TreeSet(); public String getKeys(Element element) { for(Entry e : m.entrySet()) { mapSubKey = e.getValue(); for(Entry e2 : mapSubKey.entrySet()) { setElements = e2.getValue(); for(Element elem : setElements) if(elem.equals(element)) return "Key: " + e.getKey() + " SubKey: " + e2.getKey(); } } }

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  • Many-to-Many Relationship (with properties) in Google App Engine for Java

    - by rvandervort
    I understand from the official documentation on unowned relationships that the app must use sets of Key objects on either side of the relationship. This makes perfect sense. Coming from many years of RDBM-style programming, though, I'm pretty confused about how I can model properties of that relationship itself. For example, if I have entities Category and Entry in my many-to-many relationship and would like to persist a dateAdded property, or some other data that are only relevant when both sides of the relationship are known. I suppose it would be possible to create a third class : CategoryEntry that links the two, but this seems like a kludge. What is the proposed way to model this kind of situation ?

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  • Java scanner - taking specific part of line

    - by user1290213
    Hi ive got a log file containing trace routes and pings. Ive seperated these by using if(scanner.nextLine().startsWith("64 bytes"){} so i can work with just the pings for now. All im interested in from the ping is time=XX example data line = 64 bytes from ziva.zarnet.ac.zw (209.88.89.132): icmp_seq=119 ttl=46 time=199 ms I have been reading other peoples similar questions and im not sure how to apply to mine. I literally need just the number as i will be putting them into a csv file so i can make a graph of the data.

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  • Localized text in Java

    - by Eager Learner
    My requirement is to display localized text messages in a J2EE web application. I know J2EE provides very good support for this. My question is what is the practice followed to have the localized messages stored to be used by the application. If I want to display Japanese / Chinese kind of messages which are not like English like char sets how do we get that messages/text into the properties files or Database tables.

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  • ByteArrayOutputStream to PrintWriter (Java Servlet)

    - by Thomas
    Writing generated PDF (ByteArrayOutputStream) in a Servlet to PrintWriter. I am desperately looking for a way to write a generated PDF file to the response PrintWriter. Since a Filter up the hierarchy chain has already called response.getWriter() I can't get response.getOutputStream(). I do have a ByteArrayOutputStream where I generated the PDF into. Now all I need is a way to output the content of this ByteArrayOutputStream to the PrintWriter. If anyone could give me a helping hand would be very much appreciated!

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  • Example applications and benefits of using "C" , "C++" or "Java"

    - by Waltzy
    Ok, I'm revising for my upcoming year 2 exams on a CS course and its likely something like this will come up. my question is what is an ideal application that would especially benefit from the program features of each of the three languages? I have a vague idea but getting a second opinion could really help. JavaPortability, easy - good for GUIs. C++Fast but may requite significant changes in order to be moved from system to system, good for image processing. CI'm unsure here small embedded applications? Some clarification on this would be really appreciated, thanks again StackOverflow

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