Java BitSet previousSetBit() Method

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Description

The Java BitSet previousSetBit(int fromIndex) method returns the index of the first bit that is set to true that occurs on or before the specified starting index.

Declaration

Following is the declaration for java.util.BitSet.previousSetBit() method

public int previousSetBit(int fromIndex)

Parameters

fromIndex − the index to start checking from (inclusive).

Return Value

This method returns the index of the previous set bit.

Exception

IndexOutOfBoundsException − if the specified index is negative.

Example 1

The following example shows the usage of Java BitSet previousSetBit() method. We're creating two BitSets. We're setting true values in a BitSet object using set() method call and using previousSetBit() method we're printing the previous set bit of bitsets.

package com.tutorialspoint;
import java.util.BitSet;
public class BitSetDemo {
   public static void main(String[] args) {

      // create 2 bitsets
      BitSet bitset1 = new BitSet();
      BitSet bitset2 = new BitSet();

      // assign values to bitset1
      bitset1.set(0, 6, true);

      // assign values to bitset2
      bitset2.set(2);
      bitset2.set(4);
      bitset2.set(6);
      bitset2.set(8);
      bitset2.set(10);

      // print the sets
      System.out.println("Bitset1:" + bitset1);
      System.out.println("Bitset2:" + bitset2);

      // print the previous set bit
      System.out.println(bitset1.previousSetBit(5));
      System.out.println(bitset2.previousSetBit(10));
   }
}

Let us compile and run the above program, this will produce the following result −

Bitset1:{0, 1, 2, 3, 4, 5}
Bitset2:{2, 4, 6, 8, 10}
5
10

Example 2

The following example shows the usage of Java BitSet previousSetBit() method. We're creating two BitSets using byte[] and and using previousSetBit() method we're printing the previous set bit of bitsets.

package com.tutorialspoint;
import java.util.BitSet;
public class BitSetDemo {
   public static void main(String[] args) {

      // create 2 bitsets
      BitSet bitset1 = BitSet.valueOf(new byte[] { 0, 1, 2, 3, 4, 5 });
      BitSet bitset2 = BitSet.valueOf(new byte[] { 2, 4, 6, 8, 10 });

      // print the sets
      System.out.println("Bitset1:" + bitset1);
      System.out.println("Bitset2:" + bitset2);

      // print the previous set bit
      System.out.println(bitset1.previousSetBit(42));
      System.out.println(bitset2.previousSetBit(35));
   }
}

Let us compile and run the above program, this will produce the following result −

Bitset1:{8, 17, 24, 25, 34, 40, 42}
Bitset2:{1, 10, 17, 18, 27, 33, 35}
42
35

Example 3

The following example shows the usage of Java BitSet previousSetBit() method. We're creating two BitSets using long[] and and using previousSetBit() method we're printing the previous set bit of bitsets.

package com.tutorialspoint;
import java.util.BitSet;
public class BitSetDemo {
   public static void main(String[] args) {

      // create 2 bitsets
      BitSet bitset1 = BitSet.valueOf(new long[] { 0, 1, 2, 3, 4, 5 });
      BitSet bitset2 = BitSet.valueOf(new long[] { 2, 4, 6, 8, 10 });

      // print the sets
      System.out.println("Bitset1:" + bitset1);
      System.out.println("Bitset2:" + bitset2);

      // print the previous set bit
      System.out.println(bitset1.previousSetBit(332));
      System.out.println(bitset2.previousSetBit(259));
   }
}

Let us compile and run the above program, this will produce the following result −

Bitset1:{64, 129, 192, 193, 258, 320, 322}
Bitset2:{1, 66, 129, 130, 195, 257, 259}
322
259