cmd open and close immediately while opening java

Question

I am creating a code editor for Java source files by using Java. When I click on the RUN menu, it perfectly opens cmd and run javac command, but the problem is that it immediately gets closed and I want something like pause.

This is my code:

Runtime rt = Runtime.getRuntime();
try {
    rt.exec("cmd.exe /c start java Maq");
} catch (IOException e1) {
    e1.printStackTrace();
}

How to get rid of this problem?

Javac? But in your code you have java command? Explain what do you mean by pause — shazin, Oct 05 '14 at 11:48

score 2 · Answer 1 · edited May 23 '17 at 12:00

Now that you have confirmed that you actually need javac and are working on an IDE/editor, the right way to handle compiling errors is by compiling from the JRE using javax.tools.JavaCompiler.

The JavaCompiler gives you refined control, cross platform functionality and is always there. You can take a look at the JavaDoc to get yourself started. Here's a nice example of its usage.

I have used it personally for an IDE like project and it did exactly what you would expect from an in-program compiler.

score 0 · Answer 2 · answered Oct 05 '14 at 11:49

0

The 'start' bit of your command detaches Java from the cmd process.

You're probably best off writing a batch script containing something like this:

@echo off
java Maq
pause

Then just call that batch file using Runtime.exec(...)

answered Oct 05 '14 at 11:49

Mitchell

29
1

but my code editor may have multiple tabs so shld i every time creates a batch file for evry tab to run them out?? – maq Oct 05 '14 at 12:14
1

Java is OS-independent by default, and this is very bad practice as well (no arguments ...) – msrd0 Oct 05 '14 at 12:41
maq, you could use arguments in the batch script. But msrd0 is right, and I completely agree with him, albeit no Runtime.exec call is cross platform when things like cmd.exe are involved. The proper solution is to use Java's Process functionality or as I posted as a new answer, the built in compiler – Mitchell Oct 05 '14 at 20:34

msrd0 · Answer 3 · 2017-08-07T15:02:46.830

0

To see javac's output, you can't use Runtime.exec(). Use a ProcessBuilder instead. Your code can look something like this:

ProcessBuilder pb = new ProcessBuilder("javac", "Maq.java");
pb.directory(new File("/path/to/source/code/"));

Process p = pb.start();
InputStream in = p.getInputStream(); // this is connected to the System.out from javac
int exit = p.waitFor(); // wait for javac to finish

StringBuilder text = new StringBuilder();
char[] buf = new char[1024]; int read;
while ((read = in.read(buf)) != -1)
    text.append(new String(buf, 0, read));
text.append("\n\njavac returned with exit code ").append(exit);

// display text - it now contains javac's output and its exit code
JFrame f = new JFrame("javac's output");
JTextPane tp = new JTextPane();
tp.setText(text.toString());
tp.setEditable(false);
f.setContentPane(tp);
f.setSize(500, 400); // or whatever
f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
f.setVisible(true);

edited Aug 07 '17 at 15:02

answered Oct 05 '14 at 12:41

msrd0

7,816
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@maq why don't you create a `JFrame` with a `JTextPane` (or similar) and show the text in it? – msrd0 Oct 05 '14 at 12:44
@maq Please see my edit, and javac never asks for input – msrd0 Oct 05 '14 at 12:47
i got you but i m sorry i did not mention i also want `java` command to run – maq Oct 05 '14 at 12:51
@maq How about adding a `JTextField` below the `JTextPane` to make that possible? – msrd0 Oct 05 '14 at 12:56
@maq It's not that complicated (I can provide the code if you want), but if you're looking after an OS-dependent solution, write a batch script like _Mitchell_ suggested – msrd0 Oct 05 '14 at 13:02
kindly provide plzz :) – maq Oct 05 '14 at 13:31
thn ur great thnk u so much waiting – maq Oct 05 '14 at 13:55
There is no such method called "pb.setDirectory" in ProcessBuilder class – Mert Serimer Aug 07 '17 at 08:53
@MertSerimer It looks like the `setDirectory` method was renamed to `directory` (see the javadoc link in the answer). Thanks for pointing this out, I'll edit my answer – msrd0 Aug 07 '17 at 15:02

score 0 · Accepted Answer · edited May 23 '17 at 12:00

0

Answer from this question helped me :)

Runtime rt = Runtime.getRuntime();
                try {
                    rt.exec("cmd.exe /c cd /d d: & start cmd.exe /k javac Maq.java");
                } catch (IOException e1) {
                    e1.printStackTrace();
                }

edited May 23 '17 at 12:00

Community

1
1

answered Oct 08 '14 at 02:28

maq

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3
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cmd open and close immediately while opening java

4 Answers4