UNIXでJavaコードでshell commandを呼び出し実行結果を取得

public class Test {
	
	public static void main(String[] args) throws Exception {
		try {
			//execute shell command: df -k .
			Process fileSystemDfInfo = Runtime.getRuntime().exec("df -k .");

			BufferedReader reader = new BufferedReader(
					new InputStreamReader(fileSystemDfInfo.getInputStream()));			
			String contentLine;
			while ((contentLine = reader.readLine()) != null){
				//do something with contentLine
				System.out.println(contentLine);
			}
			reader.close();
		} catch(Exception e) {
			e.printStackTrace();
		}
	}

}

import java.io.File;
import java.io.BufferedReader;
import java.io.InputStreamReader;

public class RunSystemCommand {
	public static void main(String args[]) {
		String s = null;
		// system command to run
		String cmd = "ls > fred.txt";
		// set the working directory for the OS command processor
		File workDir = new File("/dir1/dir2");

		try {
			Process p = Runtime.getRuntime().exec(cmd, null, workDir);
			int i = p.waitFor();
			if (i == 0) {
				BufferedReader stdInput = new BufferedReader(
						new InputStreamReader(p.getInputStream()));
				// read the output from the command
				while ((s = stdInput.readLine()) != null) {
					System.out.println(s);
				}
			} else {
				BufferedReader stdErr = new BufferedReader(
						new InputStreamReader(p.getErrorStream()));
				// read the output from the command
				while ((s = stdErr.readLine()) != null) {
					System.out.println(s);
				}

			}
		} catch (Exception e) {
			System.out.println(e);
		}
	}
}