'Switch statement with boolean is not working?

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);
javabooleanswitch-statement


Solution 1:[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");
}

Solution 2:[2]

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!");
    }
}

Solution 3:[3]

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.

Solution 4:[4]

In Java, Switch does NOT work with Boolean.

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

Solution 5:[5]

¯\_(?)_/¯

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

Solution 6:[6]

As the error clearly states, numbers are not booleans.

You want true and false.

Solution 7:[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.

Solution 8:[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

Solution 9:[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.

Solution 10:[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;
        ...
    }
}

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution Source
Solution 1
Solution 2 Tubig
Solution 3
Solution 4 Gagan Mani
Solution 5 Eric Aya
Solution 6 SLaks
Solution 7 Gigatron
Solution 8 Abhishek Ghosh
Solution 9 Mm Mmm
Solution 10

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