How to Convert a String Variable to a Boolean Variable in Java? [duplicate]

Question

I am very, very new at programming so sorry if this is a stupid question, but I can't find an answer anywhere.

In a program that I am working on the user can choose one of five options for problems to practice: addition, subtraction, multiplication, division, and remainders. There is a scanner that asks them to put in the fist letter of the name of the types of problems they want to practice (A or a, S or s, M or m, D or d, R or r). I want to make an if/else statement that will print out different problems depending on which one they choose.

The problem is, from what I can tell if/else statements will only work with boolean variables, but boolean variables don't like strings or string variables. I have seen ways to convert specific strings to variables, but since the user is deciding on the string, I have no way to know what they are going to choose every time. Is there anyway to convert a string variable to a boolean variable?? (i.e. the boolean variable is true when the string variable = "A")

Elliott Frisch · Accepted Answer · 2016-02-01 05:59:59Z

2

if(s) can take boolean expressions (and use boolean operators, such as or). For example, String.equals(Object) (or String.equalsIgnoreCase(String)). Something like,

if (string.equals("A") || string.equals("a")) {
    // ...
} else if (string.equalsIgnoreCase("B")) {// <-- or equalsIgnoreCase(String).
    // ...
}

answered Feb 1, 2016 at 5:59

Elliott Frisch

202k20 gold badges166 silver badges265 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Riley Carney · Accepted Answer · 2016-02-01 06:04:55Z

2

Personally, my favorite way is to use a switch statement when you're dealing with input, and while it doesn't use boolean values as you are use to in an if statement, for me it feels cleaner.

Your code would look like something such as:

switch(userInput.toLowerCase())
{
    case "a":
    // addition code
    break;
    case "s":
    // subtraction code
    break;
    case "m":
    // multiplication code
    break;
    case "d":
    // division code
    break;
    case "r":
    // remainder code
    break;
    default: // every other option besides (a, s, m, d, and r)
    // print some error, user put wrong input
    break;
}

answered Feb 1, 2016 at 6:04

Riley Carney

8605 silver badges18 bronze badges

Comments

ΦXocę 웃 Пepeúpa ツ · Accepted Answer · 2016-02-01 05:59:45Z

0

Ypu can use

java.lang.Boolean(String s)

Allocates a Boolean object representing the value true if the string argument is not null and is equal, ignoring case, to the string "true".

answered Feb 1, 2016 at 5:59

ΦXocę 웃 Пepeúpa ツ

48.4k17 gold badges77 silver badges102 bronze badges

Comments

Satej S · Accepted Answer · 2016-02-01 06:01:07Z

0

Here's what you can do.You're dealing with a fairly simple problem.

Pseudo-Code

if(input=="A")
{
Do Addition
}
if(input=="M")
{
Do Multiplication
}
else
{
Give Error
}

Essentially, you want to check if the user input is equal to a particular string. You use the double equal to operator (==) here to perform the check.If the condition is TRUE and it will enter the block.

answered Feb 1, 2016 at 6:01

Satej S

2,1561 gold badge18 silver badges22 bronze badges

Comments

René Vogt · Accepted Answer · 2016-02-01 18:02:27Z

The Point is that the if block is evaluated on the basis of any expression that results into boolean values(i.e. true or false).

So there is no need to convert a String to Boolean.

All you have to do is just check if input string meets your criteria using a method provided by String Class in java called String.equals(String) or String.equalsIgnoreCase(String);

The return type of above methods is boolean (primitive) which will be evaluated by if statement as per your requirements.

To explore String Class in java run "javap java.lang.String" on shell/bash/command prompt for programmer's guide to check out the contents of String Class

So your code will be something like

if(input.equalsIgnoreCase("a"))
{
  // Calculations for addition
}
else if(input.equalsIgnoreCase("s")) 
{
  // Calculations for Substraction
}

Instead you can use switch-case as support for String in switch-case has been included from jdk7.

Also switch-case should be faster in this case as it will not check all cases as done by else if.

switch(input)
{
    case "a":
    case "A":
        // Calculations for addition
        break;
    case "s":
    case "S"
        // Calculations for subtraction
        break;
    case "m":
    case "M":
        // Calculations for multiplication
        break;
    case "d":
    case "D":
        // Calculations for division
        break;
    case "r":
    case "R":
        // Calculations for remainder
        break;
    default: // for any other option besides above
        // whatever handling you wanna do for wrong input
        break;
}

Collectives™ on Stack Overflow

How to Convert a String Variable to a Boolean Variable in Java? [duplicate]

5 Answers 5

Comments

Comments

Comments

Comments

Comments

Linked

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

Comments

Comments

Comments

Comments

Comments

Linked

Related