Java 带return语句的开关

Question

I need to return the value of a number input by the user from the command line.

eg:

java Test 5 

1 = January

2 = February etc...

I have tried using a switch statement, however, I receive an output:

May
5

when the input from command line. I'm not sure why this is.

The output should be:

/May

Here is what I have tried so far:

class theDate {

private int month;


public theDate(int theMonth){

    month = theMonth;

}

public theDate(){

}

public int getMonth() {

    switch (month) {

      case 1: System.out.println("January"); break;

      case 2: System.out.println("February"); break;

      case 3: System.out.println("March"); break;

      case 4: System.out.println("April"); break;

      case 5: System.out.println("May"); break;

      case 6: System.out.println("June"); break;

      case 7: System.out.println("July"); break;

      case 8: System.out.println("August"); break;

      case 9: System.out.println("September"); break;

      case 10: System.out.println("October"); break;

      case 11: System.out.println("November"); break;

      case 12: System.out.println("December"); break;



        }

        return month;

}



public String getDate(String[] datePartsObj) {


        month = Integer.parseInt(datePartsObj[0]);


        return "/" + month;

    }

}


public class Test {

private MyDate myDateObj;


public Test(){

}


public static void main(String [] args) {

    String[] datePartsObj;
    datePartsObj = args[0].split("/");
    int month = Integer.parseInt(datePartsObj[0]);

    theDate myDateObj = new theDate(month);

    System.out.println(myDateObj.getMonth());

    }

}

I'm very new to Java so any help would be greatly appreciated!

Answer 1

Seems like you want to return the name of the month by checking a given number.

You have to change the method to return a String and not an int , then you can directly return the name in the matching case , like this:

public String getMonth() {
    switch (month) {
    case 1:
        // print the name of the month
        System.out.println("January");
        // and return it... same for ever other month
        return "January";
    case 2:
        System.out.println("February");
        return "February";
    case 3:
        System.out.println("March");
        return "March";
    case 4:
        System.out.println("April");
        return "April";
    case 5:
        System.out.println("May");
        return "May";
    case 6:
        System.out.println("June");
        return "June";
    case 7:
        System.out.println("July");
        return "July";
    case 8:
        System.out.println("August");
        return "August";
    case 9:
        System.out.println("September");
        return "September";
    case 10:
        System.out.println("October");
        return "October";
    case 11:
        System.out.println("November");
        return "November";
    case 12:
        System.out.println("December");
        return "December";
    // for any number less than 1 and greater than 12 throw an exception
    default:
        throw new RuntimeException("Invalid month number");
    }
}

Answer 2

Your entire workflow has 2 print statements getting executed. One inside getMonth() method(which is printing "MAY"),and other in main() method(which prints 5)

What you need to do is change the return type of getMonth() from int to String

 public String getMonth() {

    switch (month) {

      case 1: return "January";

      case 2: return "February";

      case 3: return "March";

      case 4: return "April";

      case 5: return "May";

      case 6: return "June";

      case 7: return "July";

      case 8: return "August";

      case 9: return "September";

      case 10: return "October";

      case 11: return "November";

      case 12: return "December";

        }

        return "Invalid Month";

}

This way, your workflow is going to have a single print statement in main method.