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javastringbooleanprimitive

Concatenation of Boolean and Int

Why can't i do this? I understand that concatenation of a int and a string or with boolean,(true or false) is possible, but not an addition of boolean with an int.

What exactly happens when u add a int with a boolean? Why does it show an error?

System.out.println(a.length() + a.startsWith("a"));

i also understand that the work around for this code is

System.out.println(""+a.length() + a.startsWith("a"));

which uses concatenation.

Solution

  • Because the + operation has different functions.

    In the first example you try Number + Boolean. And this doesn't make sense, so the compiler gives an error.

    In the second example you try String + Number (which is allow as String - concentation and returns a String). Afterwards you try String + boolean (which is also allowed)