這里面我們對java中的Runtime類做一個簡單的了解介紹。若不常想到無常和死，雖有絕頂的聰明，照理說也和呆子一樣。

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Runtimeo類的使用

一、得到系統內存的一些信息

@Test public void runtimeInfo() {Runtime runtime = Runtime.getRuntime();int processors = runtime.availableProcessors();long freeMemory = runtime.freeMemory();long maxMemory = runtime.maxMemory();long totalMemory = runtime.totalMemory();// processors=4, freeMemory=165713400, maxMemory=2837446656, totalMemory=192937984logger.debug("processors={}, freeMemory={}, maxMemory={}, totalMemory={}", processors, freeMemory, maxMemory, totalMemory); }

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二、得到系統的環境變量

@Test public void dirRuntimeProcess() throws IOException, InterruptedException {Process process = Runtime.getRuntime().exec("cmd.exe /c echo %JAVA_HOME%");BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(process.getInputStream()));String string = null;while ((string = bufferedReader.readLine()) != null) {System.out.println(string); // D:\Java\jdk\jdk1.8.0_152 }process.waitFor();System.out.println("return: " + process.exitValue()); // return: 0 }

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三、得到java的版本號，這個和上述的不一樣

@Test public void getJavaVersion() {try {Process process = Runtime.getRuntime().exec("javac -version");BufferedReader br = new BufferedReader(new InputStreamReader(process.getErrorStream()));String line = null;while ((line = br.readLine()) != null)System.out.println(line); // javac 1.8.0_152 process.waitFor();System.out.println("Process exitValue: " + process.exitValue());} catch (Throwable t) {t.printStackTrace();} }

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四、執行外部命令得到的結果

@Test public void execProgramC() {try {Process process = Runtime.getRuntime().exec("C:/Users/76801/Desktop/huhx.exe");BufferedReader br = new BufferedReader(new InputStreamReader(process.getInputStream()));String line = null;while ((line = br.readLine()) != null)System.out.println(line); // Hello World. process.waitFor();System.out.println("Process exitValue: " + process.exitValue());} catch (Throwable t) {t.printStackTrace();} }

huhx.c比較簡單，就是打印一句話。

#include<stdio.h>void main() {printf("Hello World."); }

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五、使用Runtime類導出mysql腳本

@Test public void execMysqldump() throws IOException, InterruptedException {String execCommand = "cmd c/ D:/Java/mysqldump.exe -uhuhx -phuhx boot_learn > D:/bootlearn.sql";System.out.println("exec command: " + execCommand);Runtime runtime = Runtime.getRuntime();Process p = runtime.exec(execCommand);StreamGobbler errorGobbler = new StreamGobbler(p.getErrorStream(), "Error");StreamGobbler outputGobbler = new StreamGobbler(p.getInputStream(), "Output");errorGobbler.start();outputGobbler.start();p.waitFor();System.out.println("successful." + p.exitValue()); }

上述也使用到了網上所說的讀出窗口的標準輸出緩沖區中的內容，仍舊沒有解決Process的waitFor阻塞問題。下面是清空緩沖區的線程代碼：

public class StreamGobbler extends Thread {InputStream is;String type;public StreamGobbler(InputStream is, String type) {this.is = is;this.type = type;}public void run() {try (InputStreamReader isr = new InputStreamReader(is);) {BufferedReader br = new BufferedReader(isr);String line = null;while ((line = br.readLine()) != null) {if (type.equals("Error")) {System.out.println("Error :" + line);} else {System.out.println("Debug:" + line);}}} catch (IOException e) {e.printStackTrace();}} }

?代碼的目標是導出mysql數據庫的腳本。沒有找到問題的解決方案，運行環境是win10，jdk1.8。

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友情鏈接

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轉載于:https://www.cnblogs.com/huhx/p/baseusejavaruntime1.html

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