1.Ping是Windows、Unix和Linux系统下的一个命令。

ping也属于一个通信协议，是TCP/IP协议的一部分。

利用“ping”命令可以检查网络是否连通，可以很好地帮助我们分析和判定网络故障。

3.Runtime.exec()：

3.1.Runtime

好，最后重点说一下Runtime，他在java.lang包下面，

/**
 * Executes the specified command and its arguments in a separate native
 * process. The new process inherits the environment of the caller. Calling
 * this method is equivalent to calling {@code exec(progArray, null, null)}.
 *
 * @param progArray
 *            the array containing the program to execute as well as any
 *            arguments to the program.
 * @return the new {@code Process} object that represents the native
 *         process.
 * @throws IOException
 *             if the requested program can not be executed.
 */
public Process exec(String[] progArray) throws java.io.IOException {
    return exec(progArray, null, null);
}

/**
 * Executes the specified command and its arguments in a separate native
 * process. The new process uses the environment provided in {@code envp}.
 * Calling this method is equivalent to calling
 * {@code exec(progArray, envp, null)}.
 *
 * @param progArray
 *            the array containing the program to execute as well as any
 *            arguments to the program.
 * @param envp
 *            the array containing the environment to start the new process
 *            in.
 * @return the new {@code Process} object that represents the native
 *         process.
 * @throws IOException
 *             if the requested program can not be executed.
 */
public Process exec(String[] progArray, String[] envp) throws java.io.IOException {
    return exec(progArray, envp, null);
}

/**
 * Executes the specified command and its arguments in a separate native
 * process. The new process uses the environment provided in {@code envp}
 * and the working directory specified by {@code directory}.
 *
 * @param progArray
 *            the array containing the program to execute as well as any
 *            arguments to the program.
 * @param envp
 *            the array containing the environment to start the new process
 *            in.
 * @param directory
 *            the directory in which to execute the program. If {@code null},
 *            execute if in the same directory as the parent process.
 * @return the new {@code Process} object that represents the native
 *         process.
 * @throws IOException
 *             if the requested program can not be executed.
 */
public Process exec(String[] progArray, String[] envp, File directory) throws IOException {
    // ProcessManager is responsible for all argument checking.
    return ProcessManager.getInstance().exec(progArray, envp, directory, false);
}

/**
 * Executes the specified program in a separate native process. The new
 * process inherits the environment of the caller. Calling this method is
 * equivalent to calling {@code exec(prog, null, null)}.
 *
 * @param prog
 *            the name of the program to execute.
 * @return the new {@code Process} object that represents the native
 *         process.
 * @throws IOException
 *             if the requested program can not be executed.
 */
public Process exec(String prog) throws java.io.IOException {
    return exec(prog, null, null);
}

/**
 * Executes the specified program in a separate native process. The new
 * process uses the environment provided in {@code envp}. Calling this
 * method is equivalent to calling {@code exec(prog, envp, null)}.
 *
 * @param prog
 *            the name of the program to execute.
 * @param envp
 *            the array containing the environment to start the new process
 *            in.
 * @return the new {@code Process} object that represents the native
 *         process.
 * @throws IOException
 *             if the requested program can not be executed.
 */
public Process exec(String prog, String[] envp) throws java.io.IOException {
    return exec(prog, envp, null);
}

/**
 * Executes the specified program in a separate native process. The new
 * process uses the environment provided in {@code envp} and the working
 * directory specified by {@code directory}.
 *
 * @param prog
 *            the name of the program to execute.
 * @param envp
 *            the array containing the environment to start the new process
 *            in.
 * @param directory
 *            the directory in which to execute the program. If {@code null},
 *            execute if in the same directory as the parent process.
 * @return the new {@code Process} object that represents the native
 *         process.
 * @throws IOException
 *             if the requested program can not be executed.
 */
public Process exec(String prog, String[] envp, File directory) throws java.io.IOException {
    // Sanity checks
    if (prog == null) {
        throw new NullPointerException("prog == null");
    } else if (prog.isEmpty()) {
        throw new IllegalArgumentException("prog is empty");
    }

    // Break down into tokens, as described in Java docs
    StringTokenizer tokenizer = new StringTokenizer(prog);
    int length = tokenizer.countTokens();
    String[] progArray = new String[length];
    for (int i = 0; i < length; i++) {
        progArray[i] = tokenizer.nextToken();
    }

    // Delegate
    return exec(progArray, envp, directory);
}

prog时需要执行的程序，怎么理解，其实很简单，就是系统的command命令，到这大家应该都清楚了，Android是Linux系统，这里的指令也就是Linux的命令了，例如ps（查看进程），ls，pwd（查看现在路径，文件等等）等等，大家都可以去试试。

*注意点：

    1、exec的String prog只能执行一条指令，如果需要执行多条指令需要放入sh脚本文件中执行或者调用多次exec函数。

    2、exec的String command不支持通配符（*）。

    3、有些指令需要指定File dir（工作目录）。

    4、默认的工作目录是根目录/。（通过执行指令pwd可查到）

    5、导出logcat日志到SD卡ziyouku目录，参数：("logcat -df logcat.log",new File("/mnt/sdcard/ziyouku/"))

    6、logcat读取权限：<uses-permission android:name="android.permission.READ_LOGS" />

好，今天就说这么多，最近在做Spingboot开发后台并发系统，所以写博客也是对之前项目的很多技术点的总结完善。