CODEWITHSUNDEEP
javaclassswitch-statementif-statement
stokkseyri
stokkseyri

Reputation: 67

Help with breaking out of if/elses?

I'm writing a protocol class, which includes a lot of if/elses..here's the class:

public class Protocol {
    Scanner scan = new Scanner(System.in);
    private static final int WAITING = 0;
    private static final int SENTREQUEST = 1;
    private static final int SENTITEMS = 2;
    private static final int ANOTHER = 3;
    private static final int CHOICE = 4;
    private int choice;

    private int state = WAITING;



    public String processInput(String theInput) {
        String theOutput = null;

        if (state == WAITING) {
            theOutput = "Do you accept the terms of agreement? Y/N?";
            state = SENTREQUEST;
        } else if (state == SENTREQUEST) {
            if (theInput.equalsIgnoreCase("y")) {

              theOutput = ": 1. program file 2. pictures 3. documentation";
              state = CHOICE;
             } else {
                theOutput = "Invalid Input!";
                state = SENTITEMS;

            }

        }
        else if (state == CHOICE) {
            choice = scan.nextInt();
            switch(choice) {
                case 1: theOutput = "show something";
                break;
                case 2: theOutput = "show something";
                break;
                case 3: theOutput = "show something";
                break;
            }
        }
        else if (state == SENTITEMS) {

              theOutput = "Want another? (y/n)";
                state = ANOTHER;

        } else if (state == ANOTHER) {

              theOutput = "Do you accept the terms of agreement? Y/N?";

            if (theInput.equalsIgnoreCase("y")) {
                theOutput ="test";
                state = SENTREQUEST;
            } else {
                theOutput = "Bye.";
                state = WAITING;
            }
        }
        return theOutput;
    }
}

It doesn't get to the switch case, and i'm sure it's an issue of breaking out of the if/elses clauses correctly but i can't find the issue.

Upvotes: 0

Views: 6767

Answers (2)

pcjuzer
pcjuzer

Reputation: 2834

Use State pattern like this:

public class Protocol {
    Scanner scan = new Scanner(System.in);

    private abstract class State { abstract String doit(String theInput); }

    private final class WAITING extends State {
      String doit(String theInput) {
         state = SENTREQUEST;
         return "Do you accept the terms of agreement? Y/N?";
      }
    }

    private final class SENTREQUEST extends State {
      String doIt(String theInput) {
        if (theInput.equalsIgnoreCase("y")) {
              state = CHOICE;
              return ": 1. program file 2. pictures 3. documentation";
             } else {
                state = SENTITEMS;
                return "Invalid Input!";
            }
      }
    }

 //TODO refactoring to State classes for all
 //        private static final int SENTITEMS = 2;
 //        private static final int ANOTHER = 3;
 //        private static final int CHOICE = 4;*/
    private int choice;

    private State state = WAITING;



    public String processInput(String theInput) {
        return state.doIt(theInput);
    }
}

Upvotes: 0

frm
frm

Reputation: 3486

To solve a similar problem, once I implemented the strategy pattern as an enum. For each strategy, you create a new value for the enum, incapsulating the code in an enum method:

public enum Strategy {

    FIRST_STRATEGY {
        public String process(String input) {
            // Implementation for first strategy
            return null;
        }       
    },

    SECOND_STRATEGY {
        public String process(String input) {
            // Implementation for second strategy
            return null;
        }       

    };

    public abstract String process(String input);

}

You can apply the chosen strategy depending on the enum value you have, actually removing the chain of if/else statements:

Strategy chosenStrategy = Strategy.FIRST_STRATEGY;
String output = chosenStrategy.process(input);

This is a solution I applied for a problem of mine, perhaps it's not the optimal or the more object-oriented one. You have to choose the right solution for your problem, but I hope that my experience can help.

Upvotes: 1

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