What is the size of a boolean variable in Java?

Question

Can any one tell the bit size of boolean in Java?

Answer 1

It depends on the virtual machine, but it's easy to adapt the code from a similar question asking about bytes in Java:

class LotsOfBooleans {     boolean a0, a1, a2, a3, a4, a5, a6, a7, a8, a9, aa, ab, ac, ad, ae, af;     boolean b0, b1, b2, b3, b4, b5, b6, b7, b8, b9, ba, bb, bc, bd, be, bf;     boolean c0, c1, c2, c3, c4, c5, c6, c7, c8, c9, ca, cb, cc, cd, ce, cf;     boolean d0, d1, d2, d3, d4, d5, d6, d7, d8, d9, da, db, dc, dd, de, df;     boolean e0, e1, e2, e3, e4, e5, e6, e7, e8, e9, ea, eb, ec, ed, ee, ef; }  class LotsOfInts {     int a0, a1, a2, a3, a4, a5, a6, a7, a8, a9, aa, ab, ac, ad, ae, af;     int b0, b1, b2, b3, b4, b5, b6, b7, b8, b9, ba, bb, bc, bd, be, bf;     int c0, c1, c2, c3, c4, c5, c6, c7, c8, c9, ca, cb, cc, cd, ce, cf;     int d0, d1, d2, d3, d4, d5, d6, d7, d8, d9, da, db, dc, dd, de, df;     int e0, e1, e2, e3, e4, e5, e6, e7, e8, e9, ea, eb, ec, ed, ee, ef; }   public class Test {     private static final int SIZE = 1000000;      public static void main(String[] args) throws Exception     {                 LotsOfBooleans[] first = new LotsOfBooleans[SIZE];         LotsOfInts[] second = new LotsOfInts[SIZE];          System.gc();         long startMem = getMemory();          for (int i=0; i < SIZE; i++)         {             first[i] = new LotsOfBooleans();         }          System.gc();         long endMem = getMemory();          System.out.println ("Size for LotsOfBooleans: " + (endMem-startMem));         System.out.println ("Average size: " + ((endMem-startMem) / ((double)SIZE)));          System.gc();         startMem = getMemory();         for (int i=0; i < SIZE; i++)         {             second[i] = new LotsOfInts();         }         System.gc();         endMem = getMemory();          System.out.println ("Size for LotsOfInts: " + (endMem-startMem));         System.out.println ("Average size: " + ((endMem-startMem) / ((double)SIZE)));          // Make sure nothing gets collected         long total = 0;         for (int i=0; i < SIZE; i++)         {             total += (first[i].a0 ? 1 : 0) + second[i].a0;         }         System.out.println(total);     }      private static long getMemory()     {         Runtime runtime = Runtime.getRuntime();         return runtime.totalMemory() - runtime.freeMemory();     } } 

To reiterate, this is VM-dependent, but on my Windows laptop running Sun's JDK build 1.6.0_11 I got the following results:

Size for LotsOfBooleans: 87978576 Average size: 87.978576 Size for LotsOfInts: 328000000 Average size: 328.0 

That suggests that booleans can basically be packed into a byte each by Sun's JVM.