I am a beginner to java, and right now start learning Java IO API. However when I run this simple BufferedWriter program, I got this error
"A JNI error has occurred, please check your installation and try
again"
package java.io.demo;
public class BufferedWriterDemo {
public static void main(String[] args) {
String directory =System.getProperty("user.home");
String fileName ="sample.txt";
String absolutePath =directory + File.separator + fileName;
String text ="This is a text sample";
try {
BufferedWriter bufferedWriter =new BufferedWriter(new FileWriter(absolutePath));
bufferedWriter.write(text);
bufferedWriter.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
I am using eclipse photon and java 8
JRE Screenshoot
Any help?
import java.io.* would work. But as per the error, you are showing shows you have an issue in your jdk installation. Please check your java version and JAVA_HOME path.
Related
I'm new to Java, and I am facing this issue in Eclipse. Even after pointing it to the correct file, it shows a file not Found Error.
I am trying to compile code from a Java file using the Java Compiler API.
The code words fine in Visual Studio with setting everything in root, But gives this error in Eclipse with all these directories.
Also, why are there three different src folders in the image?
My project structure
package com.example.app;
import javax.tools.JavaCompiler;
import javax.tools.ToolProvider;
import java.io.File;
import java.io.IOException;
public class compilier {
public static void main(String[] args) throws IOException {
JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
int result = compiler.run(null, null, null, new File("com/example/app/Code.java").getAbsolutePath());
if (result == 0)
{
System.out.println("File Compiled");
}
try {
String package_dir = "/demo/src/main/java/com/example/app";
try{
ProcessBuilder builder = new ProcessBuilder("java", package_dir.concat("/Code"));
builder.redirectErrorStream(true);
File outfile = new File((package_dir.concat("/output.txt")));
builder.redirectOutput();
builder.start();
if (outfile.length() > 3000)
{
System.out.println("Exceeded buffer limit");
System.exit(1);
}
} catch(IOException e) {
e.printStackTrace();
}
} catch (Exception err) {
System.out.println("Error!");
err.printStackTrace();
}
}
}
Error Message
Your path looks wrong. The /demo directory would need to be in the root of your current drive.
Also, the output of a Maven build is found in the target directory. The Java class files are generated there, and the resource files are copied over from src/main/res hierarchy. The .Java files are lost. You could add a Maven task to copy the .Java files but this would be very nonstandard.
Finally you need to load resource files using the classpath. There are lots of examples on the Internet. Otherwise you may end up with a project that finds the file in Eclipse but not when deployed in a .jar or .war file.
Happy hunting.
I currently want to try to create a .jar file that pinpoints to a .bat file to start a gaming server,
the Forge Modloader for the current version switched from a server startup via jar file to .bat file, and my server provider currently has no solution for it. -Small disclaimer, I haven't touched java for 6 years, which is why I may not see the obvious
For this, I found some code from Pavan.
Though, there are two problems, where I hope you may have a solution or some other workaround.
First of all, while in Intellij, "everything" works fine. main() is running, and the "Hallo World" Test .bat is opening. After compiling it to a jar, nothing happens, even with a set File Path.
Second Problem. I've tried several spots, but System.exit(0) does not work, after
int returnCode = CommandLineUtils.executeCommandLine(commandLine, systemOut, systemErr);
The code basically stops, and the process stays inactive, which could end up bad for a gaming server where I have 0 access to the needed tools to clean this up by myself... and I don't want to explain to Customer Support why there are 1000 instances of java running in the background ;)
But regardless, Thanks for your time and hopefully help as well
import java.io.File;
import java.io.OutputStreamWriter;
import org.codehaus.plexus.util.cli.CommandLineException;
import org.codehaus.plexus.util.cli.CommandLineUtils;
import org.codehaus.plexus.util.cli.Commandline;
import org.codehaus.plexus.util.cli.WriterStreamConsumer;
public class BatRunner {
public BatRunner() {
String batfile = "run.bat";
String directory = "C:\\Users\\User\\IdeaProjects";
try {
runProcess(batfile, directory);
} catch (CommandLineException e) {
e.printStackTrace();
}
}
public void runProcess(String batfile, String directory) throws CommandLineException {
Commandline commandLine = new Commandline();
File executable = new File(directory + "/" +batfile);
commandLine.setExecutable(executable.getAbsolutePath());
WriterStreamConsumer systemOut = new WriterStreamConsumer(
new OutputStreamWriter(System.out));
WriterStreamConsumer systemErr = new WriterStreamConsumer(
new OutputStreamWriter(System.out));
int returnCode = CommandLineUtils.executeCommandLine(commandLine, systemOut, systemErr);
System.exit(0);
if (returnCode != 0) {
System.out.println("Something Bad Happened!");
} else {
System.out.println("Taaa!! ddaaaaa!!");
}
}
public static void main(String[] args) {
new BatRunner();
}
}
Source: https://www.opencodez.com/java/how-to-execute-bat-file-from-java.htm/
I'm trying to use tesseract to do OCR on an image in java. I realize there are wrappers like Tess4J that provide a bunch more functionality and stuff, but I've been struggling to get it set up properly. Simply running a one-line command with Runtime is really all I need anyways since this is just a personal little project and doesn't need to work on other computers or anything.
I have this code:
import java.io.IOException;
public class Test {
public static void main(String[] args) {
System.out.println(scan("full-path-to-test-image"));
}
public static String scan(String imgPath) {
String contents = "";
String cmd = "[full-path-to-tesseract-binary] " + imgPath + " stdout";
try { contents = execCmd(cmd); }
catch (IOException e) { e.printStackTrace(); }
return contents;
}
public static String execCmd(String cmd) throws java.io.IOException {
java.util.Scanner s = new java.util.Scanner(Runtime.getRuntime().exec(cmd).getInputStream()).useDelimiter("\\A");
return s.hasNext() ? s.next() : "";
}
}
When it's compiled and run directly from terminal, it works perfectly. When I open the exact same file in eclipse, however, it gives an IOException:
java.io.IOException: Cannot run program "tesseract": error=2, No such file or directory
What's going on? Thank you for any help.
Check the working folder in the run configuration for the Test class in Eclipse. I bet it's different from the one when you run the same program from a terminal.
I've write a Java programm and packaged it the usual way in a jar-File - unfortunately is needs to read in a txt-File. Thats way the programm failed to start on other computer machines because it could not find the txt-file.
At the same time Im using many images in my programm but here there is no such problem: I "copy" the images to the eclipse home directory, so that they are packaged in the jar-File and usable through following command:
BufferedImage buffImage=ImageIO.read(ClassName.class.getClassLoader()
.getResourceAsStream("your/class/pathName/));
There is something similar for simple textfiles which then can be use as a normal new File()?
Edit
Ive try to solve my problem with this solution:
package footballQuestioner;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import javax.security.auth.login.Configuration;
public class attempter {
public static void main(String[] args) {
example ex = new example();
}
}
class example {
public example() {
String line = null;
BufferedReader buff = new BufferedReader(new InputStreamReader(
Configuration.class
.getResourceAsStream("footballQuestioner/BackUpFile")));
do {
try {
line = buff.readLine();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
} while (line != null);
}
}
But it gives always an NullPointerException...do I have forgotten something?
Here is as required my file structure of my jar-File:
You can load the file from the ClassPath by doing something like this:
ClassLoader cl = getClass().getClassLoader()
cl.getResourceAsStream("TextFile.txt");
this should also work:
getClass().getResourceAsStream(fileName);
File always points to a file in the filesystem, so I think you will have to deal with a stream.
There are no "files" in a jar but you can get your text file as a resource (URL) or as an InputStream. An InputStream can be passed into a Scanner which can help you read your file.
You state:
But it gives always an NullPointerException...do I have forgotten something?
It means that likely your resource path, "footballQuestioner/BackUpFile" is wrong. You need to start looking for the resource relative to your class files. You need to make sure to spell your file name and its extension correctly. Are you missing a .txt extension here?
Edit
What if you try simply:
BufferedReader buff = new BufferedReader(new InputStreamReader(
Configuration.class.getResourceAsStream("BackUpFile")));
I am pretty new to Java. I want to create a Java Applet that will allow my JavaScript to pass a commandline to the Java Applet. This will only ever be run on my development machine - no need to remind me what a security issue that is. The use-case is that I have an introspector for my ExtJS app that allows me to display the classes. I want to be able to click a class, pass the relevant pathname to the Applet and have that file open in Eclipse for editing.
I am using Win7x64, jre 1.7
So, to get Eclipse to open the file from the commandline the command is:
D:\Eclipse\eclipse.exe --launcher.openFile C:\mytestfile.js
This works.
I have written the Applet, self signed it and tested the say() method using the code shown below. That works. However when I run the executecmd() method, I don't get any output. If I comment out the whole try/catch block so that I am simply returning the cmd string passed in, the method works. Therefore, I suspect that I have the try catch incorrectly setup and since my Java skills and knowledge of the exceptions are primitive I am lost.
Can anyone help me please? At least to get some output returned, if not how to actually run the command line passed in?
And, I am passing the whole command line because when I have this working I would like to share it (since the Ext introspector is really useful). Other developers will be using different editors so this way they can use it by passing their specific commandline.
Thanks!
Murray
My HTML test page:
<html>
<head>
<meta charset="UTF-8">
<title>Test Run</title>
<script src="http://www.java.com/js/deployJava.js"></script>
<script>
var attributes = { id:'testapp', code:'systemcmd.Runcmd', archive:'runcmd.jar', width:300, height:50} ;
var parameters = {} ;
deployJava.runApplet(attributes, parameters, '1.6');
</script>
</head>
<body>
<p>Hello</p>
<script type="text/javascript">
//alert(testapp.say("Hello test")); // This works
var command = "D:\Eclipse\eclipse.exe --launcher.openFile C:\mytestfile.js";
alert(testapp.executecmd(command)); // Nothing returned at all.
</script>
</body>
</html>
My class:
package systemcmd;
import java.applet.Applet;
import java.io.IOException;
import java.security.AccessController;
//import java.security.PrivilegedAction;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;
public class Runcmd extends Applet {
private static final long serialVersionUID = -4370650602318597069L;
/**
* #param args
*/
public static void main(String[] args) {
}
public String say(String arg)
{
String msg[] = {null};
msg[0] = "In Say. You said: " + arg;
String output ="";
for(String str: msg)
output=output+str;
return output;
}
public String executecmd(final String cmd) throws IOException
{
final String msg[] = {null};
String output ="";
msg[0] = "In executecmd, cmd="+cmd;
try {
try {
AccessController.doPrivileged(
new PrivilegedExceptionAction() {
public Object run() throws IOException { //RuntimeException,
msg[1] = " Pre exec()";
Runtime.getRuntime().exec(cmd);
msg[2] = " Post exec()";
return null;
}
}
);
} catch (PrivilegedActionException e) {
msg[3] = " Caught PrivilegedActionException:"+ e.toString();
throw (IOException) e.getException();
}
}
catch (Exception e) {
msg[4] = " Command:" + cmd + ". Exception:" + e.toString();
}
msg[5] = " End of executecmd.";
for(String str: msg)
output=output+str;
return output;
}
}
Set Eclipse as the default consumer for .java files and use Desktop.open(File) which..
Launches the associated application to open the file.
Ok, #Andrew. Some progress, thank you!
I set the default program for *.js files to Eclipse and if I double click a file it opens in Eclipse. All good.
I then had success running the following using RunAs Java Application - the test file opened in Eclipse. Getting closer!
public class Runcmd extends Applet {
File file;
private static Desktop desktop;
private static final long serialVersionUID = -4370650602318597069L;
/**
* #param args
* #throws IOException
*/
public static void main(String[] args) throws IOException {
System.out.println("hello");
if (Desktop.isDesktopSupported()) {
desktop = Desktop.getDesktop();
}
File file = new File("C:\\sites\\test.js");
// This works if I execute it from the Eclipse RunsAs Java Application.
// ie the file is opened in Eclipse for editing.
// And, if I specify a non-existant file, it correctly throws and prints the error
try {
desktop.open(file);
} catch (Exception ioe) {
ioe.printStackTrace();
System.out.println("Error: " + ioe.toString());
}
}}
However, when I added the following method and ran it via the DeployJava.js (as per my original post above), I get the following output returned with the error appearing whether or not the jar is self signed.
Started: , Desktop is supported , Error:
java.security.AccessControlException: access denied
("java.awt.AWTPermission" "showWindowWithoutWarningBanner")
public static String openfile(String arg) {
String output = "Started: ";
File file = new File("C:\\sites\\test.js");
if (Desktop.isDesktopSupported()) {
desktop = Desktop.getDesktop();
output = output + ", Desktop is supported ";
}
try {
desktop.open(file);
} catch (Exception ioe) {
output = output + ", Error: " + ioe.toString();
}
return output + arg;
}
So, what do I need to add to get around the apparent security issue? I have read the docs and the tutorials and I am going around in circles! There seems to be a lot of conflicting advice. :-(
Thanks again,
Murray