Varying possible loss of precision
- by szupie
In Java, when you do
int b;
b = b + 1.0;
You get a possible loss of precision error. But why is it that if you do
int b;
b += 1.0;
There isn't any error?
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A good open source web crawler for indexing Specific website for specific contents?
- by Peeyush
Hello Please suggest me a good open source web crawler written in C++,JAVA or PHP. i just need to crawl/index some specific websites for specific contents(images,text,videos). i know that their are already a lot of question & answers about this topic on this website but i am a little confused after reading all of them. So i am sorry if i am repeating the same question again. -Thanks in advanceRead the article
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What is the recommended way to set GET parameters on a Restlet request?
- by Simon Nickerson
What is the recommended way of setting GET query parameters on a Restlet Request object? I think I can see how to get them out of the request using getQueryAsForm(), but how do they get set in the first place? At the moment, I am adding them manually to the URL using a StringBuilder and java.net.URLEncoder, but it seems like there should be a better way.Read the article
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How to check if an IP address is the local host on a multi-homed system?
- by MItch Branting
For a machine with multiple NIC cards, is there a convenient method in Java that tells whether a given IP address is the current machine or not. e.g. boolean IsThisMyIpAddress("192.168.220.25");Read the article
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Removing all items of a given value from a hashmap
- by Anthony Webb
So I have a java hashmap like below: hMap.put("1", "One"); hMap.put("2", "Two"); hMap.put("3", "Two"); I would like to remove ALL items where the value is "Two" If I do something like: hmap.values().remove("Two"); Only the first one is deleted, I want to remove them all, how can this be done?Read the article
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JFileChooser on OS X
- by Hamza Yerlikaya
JFileChooser looks nothing like the native widget. I seem to remember reading some hack to get it look like the native widget but searching for it know i can't seem to find it again i came across posts that suggest using java.awt.FileChooser but that class does not seem to be in the distribution. How can i make JFileChooser make look like the native widget?Read the article
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Creating a Type object corresponding to a generic type
- by Alexey Romanov
In Java, how can I construct a Type object for Map<String, String>? System.out.println(Map<String, String>.class); doesn't compile. One workaround I can think of is private Map<String, String> dummy() { throw new Error(); } Type mapStringString = Class.forName("ThisClass").getMethod("dummy", null).getGenericReturnType(); Is this the correct way?Read the article
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Reading three words and sorting them in lexicographic order
- by Derrick
I am trying to create a program that asks the User to type three words and sort them in lexicographic order. EXAMPLE; Enter three words separated by spaces: Pear Orange Apple Apple Orange Pear The program is working fine (if I attempt the above example) except for one type of combination example that I will show below. EXAMPLE; Enter three words separated by spaces: Orange Apple Pear Apple Pear Pear The program is skipping the first word (Orange) if it is supposed to appear in the middle of the three words. I believe that this line of code is affecting the program because it says that "this assigned value is never used" but I'm not sure how to fix it since I'm still an entry Java learner. middle = firstWord; Because of that line being unused, it's why Pear appeared twice. import java.util.*; public static void main(String[] args) { Scanner wordInput = new Scanner(System.in); String firstWord; String secondWord; String thirdWord; System.out.println("Enter three words separated by spaces: "); firstWord = wordInput.next(); secondWord = wordInput.next(); thirdWord = wordInput.next(); String top = firstWord; String bottom = firstWord; if( top.compareTo(secondWord) > 0) { top = secondWord; } if( top.compareTo(thirdWord) > 0) { top = thirdWord; } if( bottom.compareTo(secondWord) < 0) { bottom = secondWord; } if( bottom.compareTo(thirdWord) < 0) { bottom = thirdWord; } String middle; if( !firstWord.equals(bottom) && !firstWord.equals(top) ) { middle = firstWord; } if( !secondWord.equals(bottom) && !secondWord.equals(top) ) { middle = secondWord; } else { middle = thirdWord; } System.out.println( top ); System.out.println( middle ); System.out.println( bottom ); } } Does anyone what I am missing or doing wrong? :( Please and thank you for any help!Read the article
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Is MobiForms for Android worth investigating ?
- by Alan B
I'm working my way through the NotePad tutorial, and that's all fine - I'm not a Java programmer but it's close enough to C# (or vice versa) to make it easy to pick up. I'm surprised that there aren't any RAD tools for Android apart from Mobiforms. Is there anyone out there with experience of Mobiforms ?Read the article
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Android Calendar API vs Calendar Provider API
- by John Roberts
I'm a little bit confused about the difference between the two. An example of the Calendar API is supposedly located here: http://samples.google-api-java-client.googlecode.com/hg/calendar-android-sample/instructions.html, but the author himself suggests using the Calendar Provider API, details about which are here: http://developer.android.com/guide/topics/providers/calendar-provider.html. Can someone explain to me the difference between the two, and which would be better for me to use for a simple calendar app?Read the article
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How to discover web servers on a local network?
- by Stefan Kendall
Suppose I'm running several servers serving basic requests on my local network (say a home network, where all machines generally have an IP in the form K.K.K.x, where x is variable). Is there an easy way to discover all such servers? I would need to find each IP on the network running a particular java server application.Read the article
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Pattern for creating a database schema using JDBC
- by Space_C0wb0y
I have a Java-application that loads data from a legacy file format into an SQLite-Database using JDBC. If the database file specified does not exist, it is supposed to create a new one. Currently the schema for the database is hardcoded in the application. I would much rather have it in a separate file as an SQL-Script, but apparently there is now easy way to execute an SQL-Script though JDBC. Is there any other way or a pattern to achieve something like this?Read the article
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Annotations present at compile time but absent at runtime
- by deamon
It is possible to use Java class files which includes annotations that are not present at runtime? Example: I want to write a class with the JPA @Embeddable annotation, which would be present at compile time (maven scope: "provided"). But the annoatation definition could be absent at runtime, if the class is used outside a JPA application.Read the article
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DAO method retrieve single entry
- by London
Hello, How can I write DAO method which will return as a result only first entry from the database. For instance lets say I'm looking at Users table and I want to retrieve only the first entry, I'd declare method like: public User getFirstUser(){ //method logic } EDIT: User has primary key id if that matters at all. I apologize if this question is too simple/stupid/whatever I'm beginner with Java so I'm trying new things. thank youRead the article
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Clean multiple JTextField
- by redmarv
Hi all! I was wondering about how to clean multiple JTextField in a Java applicatio, without setting the text with an empty string for each field. Any suggestions?Read the article
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enable HeapDumpOnOutOfMemoryError in runtime
- by Schildmeijer
according to http://java.sun.com/javase/6/webnotes/trouble/TSG-VM/html/clopts.html it should be possible to enable -XX:+HeapDumpOnOutOfMemoryError using JConsole in runtime. How? I assume its somewhere under MBeans tab and the com.sun.management - HotSpotDiagnostic - Operations - setVMOptions ?Read the article
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Varying behavior for possible loss of precision
- by szupie
In Java, when you do int b; b = b + 1.0; You get a possible loss of precision error. But why is it that if you do int b; b += 1.0; There isn't any error?Read the article
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Is it safe to use connection.createStatement().executeQuery(String query);?
- by javanix
Is it safe to do connection.createStatement().executeQuery(String query);, or should each java.sql.Statement object be created and closed by "hand" on every use, even if the connection is closed in a finally block? If multiple queries are executed in one method by one connection it would use much less code if instantiating and closing each statement wasn't strictly necessary.Read the article
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Using static variables in Android
- by michael
Hi, In android, are using static variables a recommended practice? E.g, implementing a Singleton pattern in Java, I usually do: private static A the_instance; public static A getInstance() { if (the_instance == null) { the_instance = new A(); } return the_instance; } Also, when does this get cleaned up by the Android JVM? Thank you.Read the article
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Passing JSON through the URI
- by Leaf
I'm trying to create a REST based web service with data encapsulated using JSON. My problem is when I pass the string version of JSON in the URI it turns to something like this: %7B%22coal%22:100,%22ele%22:1500.1%7D. I'm wondering if there are any functions Java for converting between the escaped and unescaped versions so I can parse the string.Read the article
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find decimal in a given number
- by chandu
Hi, How can i find decimal(dot) in a given number in java. I am getting input from user, he may give integer or float value. I need to find he entered integer or float , is it possible? if yes could u tell me please. -- ThanksRead the article
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Formatting a long timestamp into a Date with JSTL
- by scubabbl
I am pulling a long timestamp from a database, but want to present it as a Date using Tags only, no embedded java in the JSP. I've created my own tag to do this because I was unable to get the parseDate and formatDate tags to work, but that's not to say they don't work. Any advice? Thanks.Read the article
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Reading POM's with it's children
- by khmarbaise
Based on the post it is mentioned (By Brett Porter) that a POM can be read. What i need is to read not only a single pom. I need to read the whole tree of pom's in a multimodule build. Starting with the root pom and it should read automatically the child pom's if it's possible? I need to do this in separate Java Code not in relationship with Maven itself.Read the article
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Convert from vector of arrays to one array
- by Afro Genius
I have a vector of float arrays i.e. Vector . I want to convert this to one float array i.e. move every element in every float[] within the vector to a new float[]. Am a bit puzzled on using the Java built in method vector.toArray() to do this. Any ideas pls?Read the article
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Why sockets does not die when server dies? Why socket dies when server is alive?
- by Roman
I try to play with sockets a bit. For that I wrote very simple "client" and "server" applications. Client: import java.net.*; public class client { public static void main(String[] args) throws Exception { InetAddress localhost = InetAddress.getLocalHost(); System.out.println("before"); Socket clientSideSocket = null; try { clientSideSocket = new Socket(localhost,12345,localhost,54321); } catch (ConnectException e) { System.out.println("Connection Refused"); } System.out.println("after"); if (clientSideSocket != null) { clientSideSocket.close(); } } } Server: import java.net.*; public class server { public static void main(String[] args) throws Exception { ServerSocket listener = new ServerSocket(12345); while (true) { Socket serverSideSocket = listener.accept(); System.out.println("A client-request is accepted."); } } } And I found a behavior that I cannot explain: I start a server, than I start a client. Connection is successfully established (client stops running and server is running). Then I close the server and start it again in a second. After that I start a client and it writes "Connection Refused". It seems to me that the server "remember" the old connection and does not want to open the second connection twice. But I do not understand how it is possible. Because I killed the previous server and started a new one! I do not start the server immediately after the previous one was killed (I wait like 20 seconds). In this case the server "forget" the socket from the previous server and accepts the request from the client. I start the server and then I start the client. Connection is established (server writes: "A client-request is accepted"). Then I wait a minute and start the client again. And server (which was running the whole time) accept the request again! Why? The server should not accept the request from the same client-IP and client-port but it does!Read the article
