Casting Boolean To Int

Question

I am going through a tutorial where so far it gives you the code below:

boolean p, q;

    System.out.println("P\tQ\tAND\tOR\tXOR\tNOT");
    p = true; q = true;

    System.out.print(p + "\t" + q + "\t");
    System.out.print((p&q) + "\t" + (p|q) + "\t");
    System.out.println((p^q) + "\t" + (!p));

    p = true; q = false;
    System.out.print(p + "\t" + q + "\t");
    System.out.print((p&q) + "\t" + (p|q) + "\t");
    System.out.println((p^q) + "\t" + (!p));

    p = false; q = true;
    System.out.print(p + "\t" + q + "\t");
    System.out.print((p&q) + "\t" + (p|q) + "\t");
    System.out.println((p^q) + "\t" + (!p));

    p = false; q = false;
    System.out.print(p + "\t" + q + "\t");
    System.out.print((p&q) + "\t" + (p|q) + "\t");
    System.out.println((p^q) + "\t" + (!p));

The task is to modify the program so that it uses 1's and 0's instead of true and false.

Im not sure if this is ment to be done by Casting Incompatible Types but I think that is the way to go as that is the section before it.

Can anyone give some advice and explanation as to why it works?

[This has been answered here already](http://stackoverflow.com/questions/3793650/convert-boolean-to-int-in-java) — asf107, Feb 02 '12 at 14:29
Think about renaming the question accordingly, because the title does not fit neither question nor answer. — mtsz, Feb 02 '12 at 14:47

Sergey Kalinichenko · Accepted Answer · 2012-02-02T14:36:19.933

3

This is not what the tutorial asks you to do. I think they want you to literally replace boolean with int, true with 1, and false with 0, like this:

int p, q;
System.out.println("P\tQ\tAND\tOR\tXOR\tNOT");
p = 1; q = 1;
System.out.print(p + "\t" + q + "\t");
System.out.print((p&q) + "\t" + (p|q) + "\t");
System.out.println((p^q) + "\t" + (1-p)); // EDIT: was !p

This will lead you to understanding of bitwise operations on integers 0 and 1.

edited Feb 02 '12 at 14:36

answered Feb 02 '12 at 14:26

Sergey Kalinichenko

714,442
84
1,110
1,523

When I try this I get an error for `(!p)` saying `The operator ! is undefined for the argument type(s) int` the book does state that this may be a bit more complicated than first thought. – Matt Feb 02 '12 at 14:29
@Matt There is no unary equivalent to the `boolean` `!` (`~` flips all bits, not just the last one). the simplest way to achieve the result you are looking for is with `(1-p)` – Sergey Kalinichenko Feb 02 '12 at 14:35

score 2 · Answer 2 · answered Dec 07 '12 at 17:29

This was my solution //Logic table using 1 and 0

class LogicOpTable {

public static void main(String args[]) {

   int p, q;

   System.out.println("P\tQ\t"+
             "AND\tOR\tXOR\tNOT");
   for (p = 1; p >= 0; p--) {
    for (q = 1; q >= 0; q--) {

   System.out.println(p + "\t" + q + "\t" +
             (p & q) + "\t" + (p | q) + 
                     "\t" + (p ^ q) + "\t" + (1 - p));
     }
  }

} }

score 1 · Answer 3 · answered Feb 02 '12 at 14:25

1

You can't cast a boolean to an int. These are completely different types.

But you can write a utility method booleanToInt(boolean b) which transforms a boolean into an int.

answered Feb 02 '12 at 14:25

JB Nizet

678,734
91
1,224
1,255

score 1 · Answer 4 · answered Feb 02 '12 at 14:30

1

Just use the ternary operator:

int logicalInt = boolVal? 1 : 0;

where "boolVal" is your boolean variable.

answered Feb 02 '12 at 14:30

eternaln00b

1,043
9
18

This hasn't been coverd in the book yet so I don't think this is the way to go :S – Matt Feb 02 '12 at 14:33

score 1 · Answer 5 · answered Feb 02 '12 at 14:41

You can use integers together with bitwise operators:

int p, q;

System.out.println("P\tQ\tAND\tOR\tXOR\tNOT");
p = 1;
q = 1;

System.out.print(p + "\t" + q + "\t");
System.out.print((p & q) + "\t" + (p | q) + "\t");
System.out.println((p ^ q) + "\t" + (1-p));

p = 1;
q = 0;
System.out.print(p + "\t" + q + "\t");
System.out.print((p & q) + "\t" + (p | q) + "\t");
System.out.println((p ^ q) + "\t" + (1-p));

p = 0;
q = 1;
System.out.print(p + "\t" + q + "\t");
System.out.print((p & q) + "\t" + (p | q) + "\t");
System.out.println((p ^ q) + "\t" + (1-p));

p = 0;
q = 0;
System.out.print(p + "\t" + q + "\t");
System.out.print((p & q) + "\t" + (p | q) + "\t");
System.out.println((p ^ q) + "\t" + (1-p));

Returns:

P   Q   AND OR  XOR NOT
1   1   1   1   0   0
1   0   0   1   1   0
0   1   0   1   1   1
0   0   0   0   0   1

score 0 · Answer 6 · answered Feb 02 '12 at 14:26

0

You can't cast directly from a boolean to an int in Java. I would add a method along the lines of

public int getBoolValue(boolean b) {
 return b ? 1 : 0

}

answered Feb 02 '12 at 14:26

Jaloopa

722
1
6
21

score 0 · Answer 7 · edited Jul 24 '12 at 13:01

0

You cannot cast int to boolean in java. Think of using

boolean x = p & q;
boolean y = p | q;

(x ? 1 : 0)

For example

System.out.print((p&q) + "\t" + (p|q) + "\t");

May become:

System.out.print(x + "\t" + y + "\t");

edited Jul 24 '12 at 13:01

Eliran Malka

15,821
6
77
100

answered Feb 02 '12 at 14:26

jestem_wojtek

81
3

score 0 · Answer 8 · answered Feb 02 '12 at 14:27

0

It looks like you just need to declare your variables as ints and assign 0 and 1 to p and q, and make sure you're using java's bitwise operators in all cases (at first glance it looks like you are). More info on bitwise operation from wikipedia.

answered Feb 02 '12 at 14:27

Raphael

1,701
15
26

When I try this I get an error for `(!p)` saying `The operator ! is undefined for the argument type(s) int` the book does state that this may be a bit more complicated than first thought. – Matt Feb 02 '12 at 14:30
As other people have said, you need to do 1-p instead of !p. – Raphael Mar 12 '12 at 15:18

Casting Boolean To Int

8 Answers8