How to make an input loop in the method?

Question

When I input motherHeight and fatherHeight then they will calculate the height of the child. But how do I add a loop so when the height of the child is zero or less, that should give an error message and try again?

import java.util.Scanner;

public class estimateHeight {
    private static Scanner kb = new Scanner(System.in);
    private static Scanner kbNum = new Scanner(System.in);

    public static void calculateHeight(char gender, float motherHeight, float fatherHeight ) {
        float height = 0;
        if(gender == 'm' || gender == 'M')
            height = ((motherHeight * 13/12) + fatherHeight )/2;
        else
            height = ((fatherHeight * 12/13) + motherHeight)/2;

        if(height <= 0) {
            System.out.println("Invalid inputs, please reneter: " );
            calculateHeight(gender, motherHeight, fatherHeight);
        }
        else
            System.out.println("The child's height is: " + height);
    }

    public static void main(String[] args) {
        System.out.println("Estimating the Adult Height of a Child. Press Q or -1 to quit.\n");

        String genderSelect;
        float fatherHeight, motherHeight;

        System.out.print("Gender? (m/f): ");
        genderSelect = kb.nextLine();
        if(genderSelect.equalsIgnoreCase("q"))
            System.exit(0);
        while(!(genderSelect.equalsIgnoreCase("m") || genderSelect.equalsIgnoreCase("f"))) {
            System.out.print("Invalid. Gender? (m/f): ");
            genderSelect = kb.nextLine();
        }

        System.out.print("Father's height? ");
        fatherHeight = kbNum.nextFloat();
        if(fatherHeight == -1)
            System.exit(0);

        System.out.print("Mother's height? ");
        motherHeight = kbNum.nextFloat();
        if(motherHeight == -1)
            System.exit(0);

        calculateHeight(genderSelect.charAt(0), motherHeight, fatherHeight);
    }
}

What language are you using? That ought to be one of the tags you apply to your question. I could guess at java, but I shouldn't have to. — Damien_The_Unbeliever
– Damien_The_Unbeliever, Commented May 23, 2013 at 13:29
Didnt understood your gender condition gender == 'm' || gender == 'M'. What does it mean? — DevelopmentIsMyPassion
– DevelopmentIsMyPassion, Commented May 23, 2013 at 13:32
emm, you dont compare strings like that. should be foo.equals() — Maciej Cygan
– Maciej Cygan, Commented May 23, 2013 at 13:48
@MaciejCygan But you do compare char's like that. And those are char's. '' indicates a char (also ...(char gender,...), "" would be a string. — Bernhard Barker
– Bernhard Barker, Commented May 23, 2013 at 13:59

Adarsh · Accepted Answer · 2013-05-23 14:45:21Z

Use a do -while loop as follows to achieve this.

import java.util.Scanner;

public class estimateHeight {
private static Scanner kb = new Scanner(System.in);
private static Scanner kbNum = new Scanner(System.in);

public static boolean calculateHeight(char gender, float motherHeight, float fatherHeight ) {
    float height = 0;
    if(gender == 'm' || gender == 'M')
        height = ((motherHeight * 13/12) + fatherHeight )/2;
    else
        height = ((fatherHeight * 12/13) + motherHeight)/2;

    if(height <= 0) {
        System.out.println ("Invalid details. Please Re-enter. ");
       return true;
    }
    else{            
        System.out.println("The child's height is: " + height);
        return false;
    }
}

public static void main(String[] args) {
boolean check;
    do{
        System.out.println("Estimating the Adult Height of a Child. Press Q or -1 to quit.\n");
        String genderSelect;
        float fatherHeight, motherHeight;

        System.out.print("Gender? (m/f): ");
        genderSelect = kb.nextLine();
        if(genderSelect.equalsIgnoreCase("q"))
            System.exit(0);
        while(!(genderSelect.equalsIgnoreCase("m") || genderSelect.equalsIgnoreCase("f"))) {
            System.out.print("Invalid. Gender? (m/f): ");
            genderSelect = kb.nextLine();
        }

        System.out.print("Father's height? ");
        fatherHeight = kbNum.nextFloat();
        if(fatherHeight == -1)
            System.exit(0);

        System.out.print("Mother's height? ");
        motherHeight = kbNum.nextFloat();
        if(motherHeight == -1)
            System.exit(0);

        check = calculateHeight(genderSelect.charAt(0), motherHeight, fatherHeight);
    }while(check);
    }

}

Bernhard Barker · Accepted Answer · 2013-05-23 13:43:12Z

0

Use recursion, something like below should work

public static void calculateHeight(char gender, float motherHeight, float fatherHeight) {
    float height = 0;
    if(gender == 'm' || gender == 'M') {
        height = ((motherHeight * 13/12) + fatherHeight)/2;
    }
    else {
        height = ((fatherHeight * 12/13) + motherHeight)/2;
    }
    if(height <= 0)
    {// recurse here
       System.out.println("Invalid inputs, please reneter: " );
        //read the inputs here, and call recursively this method     
        calculateHeight(gender, motherHeight, fatherHeight);
    }
    else
    {
        System.out.println("The child's height is: " + height);
    }
}

edited May 23, 2013 at 13:43

Bernhard Barker

55.7k14 gold badges111 silver badges143 bronze badges

answered May 23, 2013 at 13:36

Gangadhar Heralgi

2191 silver badge6 bronze badges

3 Comments

Denise Skidmore Over a year ago

Recursion has it's uses, but here that could use up a lot of extra memory to do something as easily done in a loop.

Shuvo0o Over a year ago

It doesn't work. I'll post the full code if you need to check it.

Bernhard Barker Over a year ago

+1 @Denise. Recursion should never be used for something like this. Prefer a loop like in Leo's answer.

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