OnJava8-Examples/collectiontopics/Bits.java

// collectiontopics/Bits.java
// (c)2021 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.
// Demonstration of BitSet
import java.util.*;

public class Bits {
  public static void printBitSet(BitSet b) {
    System.out.println("bits: " + b);
    StringBuilder bbits = new StringBuilder();
    for(int j = 0; j < b.size() ; j++)
      bbits.append(b.get(j) ? "1" : "0");
    System.out.println("bit pattern: " + bbits);
  }
  public static void main(String[] args) {
    Random rand = new Random(47);
    // Take the LSB of nextInt():
    byte bt = (byte)rand.nextInt();
    BitSet bb = new BitSet();
    for(int i = 7; i >= 0; i--)
      if(((1 << i) &  bt) != 0)
        bb.set(i);
      else
        bb.clear(i);
    System.out.println("byte value: " + bt);
    printBitSet(bb);

    short st = (short)rand.nextInt();
    BitSet bs = new BitSet();
    for(int i = 15; i >= 0; i--)
      if(((1 << i) &  st) != 0)
        bs.set(i);
      else
        bs.clear(i);
    System.out.println("short value: " + st);
    printBitSet(bs);

    int it = rand.nextInt();
    BitSet bi = new BitSet();
    for(int i = 31; i >= 0; i--)
      if(((1 << i) &  it) != 0)
        bi.set(i);
      else
        bi.clear(i);
    System.out.println("int value: " + it);
    printBitSet(bi);

    // Test bitsets >= 64 bits:
    BitSet b127 = new BitSet();
    b127.set(127);
    System.out.println("set bit 127: " + b127);
    BitSet b255 = new BitSet(65);
    b255.set(255);
    System.out.println("set bit 255: " + b255);
    BitSet b1023 = new BitSet(512);
    b1023.set(1023);
    b1023.set(1024);
    System.out.println("set bit 1023: " + b1023);
  }
}
/* Output:
byte value: -107
bits: {0, 2, 4, 7}
bit pattern: 101010010000000000000000000000000000000000
0000000000000000000000
short value: 1302
bits: {1, 2, 4, 8, 10}
bit pattern: 011010001010000000000000000000000000000000
0000000000000000000000
int value: -2014573909
bits: {0, 1, 3, 5, 7, 9, 11, 18, 19, 21, 22, 23, 24,
25, 26, 31}
bit pattern: 110101010101000000110111111000010000000000
0000000000000000000000
set bit 127: {127}
set bit 255: {255}
set bit 1023: {1023, 1024}
*/