在cmd使用Java扫描器

Question

How to read data from cmd using

i used this method and it works fine until it arrive to user input and the debugger get into hasnext and hang

public String readCMD() {
    try {
        Scanner sc =new Scanner(in);
        StringBuilder sb = new StringBuilder();
        String ch ;
        while (sc.hasNext()) {
            ch = sc.next();
            System.out.print(ch);
            sb.append(ch);

        }
        return sb.toString();
    } catch (Exception e) {
        System.out.println(e.getCause());
    }
    return null;
}

Answer 1

Try this

public String readCMD() {
    try {
        Scanner sc = new Scanner(System.in);
        StringBuilder sb = new StringBuilder();
        String ch;
        while (sc.hasNext()) {
            ch = sc.next();
            System.out.print(ch);
            sb.append(ch);

        }
        return sb.toString();
    } catch (Exception e) {
        System.out.println(e.getCause());
    }
    return null;
}

Answer 2

Try using nextLine() :

while (!(ch = sc.nextLine()).equals("")) {
     System.out.print(ch);
     sb.append(ch);
}

This way you read in a loop until you read an empty string...

Answer 3

You need to break out the loop using some condition, here below if user enter "exit" as input then it will break out:

public String readCMD() {
    try {
        Scanner sc =new Scanner(in);
        StringBuilder sb = new StringBuilder();
        String ch ;
        while (sc.hasNext()) {
            ch = sc.next();
            System.out.print(ch);
            sb.append(ch);
            if(ch.equals("exit")) {
              break;
            }

        }
        return sb.toString();
    } catch (Exception e) {
        System.out.println(e.getCause());
    }
    return null;
}