java使用Runtime执行系统命令遇到的问题

    public Process exec(String command, String[] envp, File dir)
        throws IOException {
        if (command.length() == 0)
            throw new IllegalArgumentException("Empty command");
 
        StringTokenizer st = new StringTokenizer(command);
        String[] cmdarray = new String[st.countTokens()];
        for (int i = 0; st.hasMoreTokens(); i++)
            cmdarray[i] = st.nextToken();
        return exec(cmdarray, envp, dir);
    }

import java.io.File;
import java.io.IOException;
import java.util.StringTokenizer; 
public class GxExec {
    private static GxExec gxExec = new GxExec(); 
    public static GxExec getGxExec() {
        return gxExec;
    }
 
    private GxExec() {} 
    public Process exec(String[] cmdarray, String[] envp, File dir)
            throws IOException {
        return new ProcessBuilder(cmdarray)
                .start();
    }
 
    public Process exec(String command, String delim)
        throws IOException {
        if (command.length() == 0) {
            throw new IllegalArgumentException("Empty command");
        }
 
        StringTokenizer st = new StringTokenizer(command, delim);
        String[] cmdarray = new String[st.countTokens()];
        for (int i = 0; st.hasMoreTokens(); i++) {
            cmdarray[i] = st.nextToken();
            System.out.println(cmdarray[i]);
        }
        return exec(cmdarray, null, null);
    } 
}

javap -l xxx > output.txt

Process p = Runtime.getRuntime().exec(new String[]{"/bin/sh","-c","javap -l xxx > output.txt"});
rm -rf name*
Process p = Runtime.getRuntime().exec(new String[]{"/bin/sh","-c","rm -rf name*"});