Admin: 1 версия

2010-06-01T07:00:47Z

1 версия

в 18:01, 31 мая 2010

2010-05-31T18:01:46Z

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== Calculate process elapsed time ==



<source lang="java">

public class Main {
public static void main(String[] args) {
long start = System.nanoTime();
System.out.println("Start: " + start);
for (int i = 0; i < 100; i++) {
for (int j = 0; j < 100; j++) {
System.out.println("asdf");
}
}
long end = System.nanoTime();
System.out.println("End : " + end);
long elapsedTime = end - start;
System.out.println(elapsedTime + " nano seconds");
}
}

</source>



== Command and its arguments supplied in an array ==



<source lang="java">

public class Main {
public static void main(String[] argv) throws Exception {
String[] commands = new String[] { "grep", "hello world", "/tmp/f.txt" };
commands = new String[] { "grep", "hello world", "c:\\f.txt" };
Process child = Runtime.getRuntime().exec(commands);
}
}

</source>



== Determine when the application is about to exit ==



<source lang="java">

public class Main {
public static void main(String[] argv) throws Exception {
Runtime.getRuntime().addShutdownHook(new Thread() {
public void run() {
System.out.println("Do shutdown work ...");
}
});
}
}

</source>



== Execute a command from code ==



<source lang="java">

public class Main {
public static void main(String[] argv) throws Exception {
// Execute a command without arguments
String command = "ls";
Process child = Runtime.getRuntime().exec(command);
// Execute a command with an argument
command = "ls /tmp";
child = Runtime.getRuntime().exec(command);
}
}

</source>



== Execute a command with an argument that contains a space ==



<source lang="java">

public class Main {
public static void main(String[] argv) throws Exception {
String[] commands = new String[] { "grep", "hello world", "/tmp/f.txt" };
commands = new String[] { "grep", "hello world", "c:\\f.txt" };
Process child = Runtime.getRuntime().exec(commands);
}
}

</source>



== Execute a command with an argument that contains a space: use array ==



<source lang="java">

public class Main {
public static void main(String[] argv) throws Exception {

String[] commands = new String[] { "grep", "hello world", "/tmp/f.txt" };
commands = new String[] { "grep", "hello world", "c:/f.txt" };
Process child = Runtime.getRuntime().exec(commands);
}
}

</source>



== Execute a command with more than one argument ==



<source lang="java">

public class Main {
public static void main(String[] argv) throws Exception {
// Execute a command with an argument that contains a space
String[] commands = new String[] { "grep", "hello world", "/tmp/f.txt" };
commands = new String[] { "grep", "hello world", "c:\\f.txt" };
Process child = Runtime.getRuntime().exec(commands);
}
}

</source>



== Execute system command ==



<source lang="java">

import java.io.IOException;
public class Main {
public static void main(String[] args) throws IOException {
String cmd = "cmd.exe /c start ";
// String file = "c:\\version.txt";
// String file = "http://www.google.ru";
// String file = "c:\\";
// String file = "mailto:author@my.ru";
String file = "mailto:";
Runtime.getRuntime().exec(cmd + file);
}
}

</source>



== From Runtime.exec() to ProcessBuilder ==



<source lang="java">

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.Arrays;
public class Main {
public static void main(String args[]) throws IOException {
Runtime runtime = Runtime.getRuntime();
Process process = runtime.exec(args);
InputStream is = process.getInputStream();
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);
String line;
System.out.printf("Output of running %s is:", Arrays.toString(args));
while ((line = br.readLine()) != null) {
System.out.println(line);
}
}
}

</source>



== Get amount of free memory within the heap in bytes. ==



<source lang="java">

public class Main {
public static void main(String[] argv) {
long heapFreeSize = Runtime.getRuntime().freeMemory();
System.out.println(heapFreeSize);
}
}

</source>



== Get current size of heap in bytes ==



<source lang="java">

public class Main {
public static void main(String[] argv) {
long heapSize = Runtime.getRuntime().totalMemory();
System.out.println(heapSize);
}
}

</source>



== Get maximum size of heap in bytes. ==



<source lang="java">

public class Main {
public static void main(String[] argv) {
long heapMaxSize = Runtime.getRuntime().maxMemory();
System.out.println(heapMaxSize);
}
}

</source>



== Get Number of Available Processors ==



<source lang="java">

public class Main {
public static void main(String[] args) {
Runtime runtime = Runtime.getRuntime();
int nrOfProcessors = runtime.availableProcessors();
System.out.println("Number of processors available to the Java Virtual Machine: "
+ nrOfProcessors);
}
}
// Number of processors available to the Java Virtual Machine: 2

</source>



== Getting the Size of the Java Memory Heap ==



<source lang="java">

public class Main {
public static void main(String[] argv) throws Exception {
long heapSize = Runtime.getRuntime().totalMemory();
long heapMaxSize = Runtime.getRuntime().maxMemory();
long heapFreeSize = Runtime.getRuntime().freeMemory();
}
}

</source>



== Launch a Unix script with Java ==



<source lang="java">

public class Main {
public static void main(String[] argv) throws Exception {
String[] cmd = { "/bin/sh", "-c", "ls > hello" };
Runtime.getRuntime().exec(cmd);
}
}

</source>



== Minimize all programs on Windows to show the Desktop ==



<source lang="java">

public class Main {
public static void main(String args[]) throws Exception {
Runtime.getRuntime().exec(
new String[] {
"cmd.exe",
"/c",
"\"" + System.getenv("APPDATA")
+ "\\Microsoft\\Internet Explorer\\Quick Launch\\Show Desktop.scf" + "\"" });
}
}

</source>



== Read all information that the child process sends to its standard output stream ==



<source lang="java">

import java.io.InputStream;
class Run2 {
public static void main(String[] args) throws java.io.IOException {
if (args.length != 1) {
System.err.println("usage: java Run pathname");
return;
}
Process p = Runtime.getRuntime().exec(args[0]);
InputStream is = p.getInputStream();
int b;
while ((b = is.read()) != -1)
System.out.print((char) b);
try {
System.out.println("Exit status = " + p.waitFor());
} catch (InterruptedException e) {
}
}
}

</source>



== Read output from a Command execution ==



<source lang="java">

import java.io.InputStream;
public class Main {
public static void main(String[] argv) throws Exception {
String command = "ls";
Process child = Runtime.getRuntime().exec(command);
InputStream in = child.getInputStream();
int c;
while ((c = in.read()) != -1) {
System.out.println((char) c);
}
in.close();
}
}

</source>



== Registering Shutdown Hooks for Virtual Machine ==



<source lang="java">

public class Main implements Runnable {
public void run() {
System.out.println("Shutting down");
}
public static void main(String[] arg) {
Runtime runTime = Runtime.getRuntime();
Main hook = new Main();
runTime.addShutdownHook(new Thread(hook));
}
}

</source>



== Runtime.getRuntime().exec ==



<source lang="java">

class Run1 {
public static void main(String[] args) throws java.io.IOException {
if (args.length != 1) {
System.err.println("usage: java Run pathname");
return;
}
Process p = Runtime.getRuntime().exec(args[0]);
try {
System.out.println("Exit status = " + p.waitFor());
} catch (InterruptedException e) {
}
}
}

</source>



== Send an Input to a Command ==



<source lang="java">

import java.io.OutputStream;
public class Main {
public static void main(String[] argv) throws Exception {
String command = "cat";
Process child = Runtime.getRuntime().exec(command);
OutputStream out = child.getOutputStream();
out.write("some text".getBytes());
out.close();
}
}

</source>

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Admin: 1 версия

в 18:01, 31 мая 2010