在 java 中需要通过以下任务从命令提示符中获取数据并显示在控制台上

Question

I'm chan beginner for Java developer one of my Interviewer asked this question on Interview I failed and i want to learn this so please share the knowledge if you know. In java need to fetch data from command Prompt and show on console by following tasks

open command prompt run as administrator type ( C:\Windows\system32.netstat -an ) It will show 4 columns like

Proto  Local Address        Foreign Address             State)
 TCP    0.0.0.0:135            0.0.0.0:0              LISTENING
 TCP    0.0.0.0:445            0.0.0.0:0              LISTENING
 TCP    0.0.0.0:554            0.0.0.0:0              LISTENING
 UDP    0.0.0.0:3702           *:*
 UDP    0.0.0.0:3702           *:*
 UDP    0.0.0.0:3702           *:*

like this more line

Task 1 Fetch data from command prompt show on console only the TCP details

TCP    0.0.0.0:135            0.0.0.0:0              LISTENING
TCP    0.0.0.0:445            0.0.0.0:0              LISTENING
TCP    0.0.0.0:554            0.0.0.0:0              LISTENING

Task 2 Fetch data from command prompt show on console only unique local address from Local Address column

0.0.0.0:135
0.0.0.0:445
0.0.0.0:554
0.0.0.0:3702

Task 3 Fetch data from command prompt show on console group by State column and count it

LISTENING = 3

I tried like,whats the exact correct methodology

    String s1= null;
    String s2= null;
    InputStream i=Runtime.getRuntime().exec("netstat -an").getInputStream();
    Scanner scan=new Scanner(i).useDelimiter("\\"+"\n"+"\n");
    s1=scan.hasNext()?scan.next():null;
    List<String> l=new ArrayList<String>();
    try {
        l.add(s1.replaceAll("Active Connections\r\n"
            + "\r\n"
            + "  Proto  Local Address          Foreign Address        State", ""));
        for(String a:l) {
            System.out.println(a);
        }
    }catch(Exception e){
        e.printStackTrace();
    }

Answer 1

You can get the output using Process class, like below:

    ProcessBuilder builder = new ProcessBuilder();
    builder.command("cmd.exe", "/c", "netstat -an");
    Process process = builder.start();
    BufferedReader reader = new BufferedReader(
        new InputStreamReader(process.getInputStream()));

Then handling that data is really up to you, there are multiple ways to acheive the goals:

    List<String[]> output = reader.lines()
            .map(line -> line.trim().split("\\s+"))
            .collect(Collectors.toList());


    List<String> task1 = output.stream()
            .filter(line -> line[0].equals("TCP"))
            .map(line -> String.join(" ", line))
            .collect(Collectors.toList());

    List<String> task2 = output.stream()
            .filter(line -> line[0].equals("TCP"))
            .filter(line -> distinctByValue(line[1]))
            .map(line -> String.join(" ", line))
            .collect(Collectors.toList());

I know the tasks solution are not perfect. Those are just a quickly written examples to show how to handle the data from reader .