Switch statement with boolean is not working?

Question

Why is my compiler telling me:

Incompatible Types:

Required: Boolean

Found: Int

under case 0 & case 1

---

For instance:

    public void test(boolean isOn){
    switch (isOn){
        case 0:
            if (isOn){
                System.out.println("its on");
            }
            break;
        case 1:
            if (!isOn){
                System.out.println("its off");
            }
            break;
        default:
            System.out.println("I don't know!");
    }

}

Driver Class:

Club me = new Club();
me.test(true);

Corespondent

Your switch and if are redundant. – Unbodied

I know its just so I can at least see how it works, I'm only learning this – Corespondent

Boolean values - true, false, FILE_NOT_FOUND! In Java, a boolean can only have two values - true, and false. Your default case will never be reached (and most people would likely use an if statement). Now, Boolean (note the capital 'B') can be null (at which point "I don't know" makes sense), but you're not using that here... – Lise

It's Java's 'feature' proving lazy compiler makes programmer write more in my view. – Parachute

Answer 1

You are switching on boolean type, and your cases are using int types. But even though you change your cases to have boolean types, that wouldn't work. You cannot switch on boolean type. And that wouldn't make any sense as using an if-else would be easier anyways:

if (isOn) {
    System.out.println("its on");
} else {
    System.out.println("its off");
}

Note that there is no "I don't know!" case here. A boolean type can have either true or false value. This is another reason, why switch-case is not for boolean type. There is no default case.

You can also condense it to a single statement by using a conditional expression:

public void test(boolean isOn) {
    System.out.println(isOn ? "its on" : "its off");
}

Jadda

I did the changes now under switch (isOn) its saying Found: Boolean, Required: Char, Byte, short or int – Corespondent

@someone You can't switch on boolean type, but only int types, String, or enum types. – Jadda

Switching on true is actually more useful that you make it seem. Go uses it all the time code.google.com/p/go-wiki/wiki/Switch#Missing_expression – Mittiemittimus

Answer 2

¯\(ツ)/¯

switch (Boolean.hashCode(isOn)) {
    case 1231 -> System.out.println("its on");
    case 1237 -> System.out.println("its off");
}

Angst

Bit late to the party, but made me laugh :D – Pneumoencephalogram

Answer 3

Just convert the boolean to number of 1 and 0.

public void test(boolean isOn){
    int trueOrFalse;
    if(isOn == true){
      trueOrFalse = 1;
    }else{
      trueOrFalse = 0;
    }
    switch (trueOrFalse){
        case 1:
            if (isOn){
                System.out.println("its on");
            }
            break;
        case 0:
            if (!isOn){
                System.out.println("its off");
            }
            break;
        default:
            System.out.println("I don't know!");
    }
}

Renie

Answer 4

switch (isOn): switching boolean and want to case with int e.g., case 0!

According to the JLS section 14.11: for a switch ( Expression ) SwitchBlock:

Expression can only be char, byte, short, int, Character, Byte, Short, Integer, String, or an enum type other wise a compile-time error occurs.

According to the specification followings are also must be true:

1. Every case constant expression associated with a switch statement must be assignable to the type of the switch Expression.
2. No two of the case constant expressions associated with a switch statement may have the same value.
3. No switch label is null.
4. At most one default label may be associated with the same switch statement

Hence, switch expression can't be float, double or boolean. TO answer the question why?: boolean true false are meaningful using with if-else, e.g., if(true) then do. Floating point numbers (float, double) are not a good candiadtes for switch as exact comparison is often broken by rounding errors. e.g. 0.11 - 0.1 == 0.01 is false.

Abortifacient

Answer 5

In Java, Switch does NOT work with Boolean.

Accepted variable types are : char,byte,short,int,String,Character,Byte,Short,Integer,enum

Choiseul

Answer 6

As the error clearly states, numbers are not booleans.

You want true and false.

Unbodied

Answer 7

This is not C++ where 1 and 0 get implicitly converted to/from true and false. Switching on boolean is also a waste of time even if you could do it; just write a simple if/else statement, or use the ? : construct.

Expositor

Answer 8

In Java switch works only with integer literals and those which could be possibly promoted to integer literals such as char.

Moreover in Java boolean type has only two values either true or false. This is unlike the situation in C/C++ where true is any value not equals to zero and false is zero.

Moreover your code is a bit redundant

Guay

As previously stated: Accepted variable types are : char,byte,short,int,String,Character,Byte,Short,Integer,enum. One can not switch off of Boolean or boolean, as how would one define a default case of neither True or False? – Grenoble

Answer 9

You can not use boolean on switch statements. it is no point to use switch when the statement is true or false. it is easy to use if-else.

Spondaic

Answer 10

Imho switch with boolean would make sense if you could use expressions for case checks instead of if else trees or continues in a loop (maybe I'm wrong that it's a benefit), e.g.:

class Testomatoe
{
    private final String country;
    private final String sort;
    private final int pricePerKiloEUCent;
    
    public Testomtoe
    (   final String country,
        final String sort,
        final int pricePerKiloEUCent
    )
    {
        this.country = country;
        this.sort = sort;
        this.pricePerKiloEUCent = pricePerKiloEUCent;
    }
    
    //get...
}


List<Testomataoe> offers = ...
String country;
String sort
int price;

for( Testomatoe tom : offers )
{
    country = tom.getCountry();
    sort = tom.getSort();
    price = tom.getPricePerKiloEUCent();
    
    switch( true )
    {
        case price < 100:
            addToQueryQuality( tom );
            break;

        case isUrgent( sort ) && price < 300:
            adddToPriOrder( tom );
            break;

        case !country.equals( "Somewheria" ) && price <= 200:
            addToOrder( tom );
            break;

        case country.equals( "Island" ) && sort.equals( "BlueFrost" ) && price < 600:
            addToAcceptable( tom );
            break;
        ...
    }
}

Frecklefaced

Answer 11

Switch case does not support to use Boolean ,long,float,double. It supports only primitive data types such as char,int,byte ,short and non primitive String data types....

Claycomb

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