Bit Manipulation

Java/5_Bit Manipulation/BitOperations.java

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+public class BitOperations {
+    //Get ith Bit
+    public static int getIthBit(int n, int i) {
+        int bitMask = 1<<i;
+        return (n & bitMask) == 0 ? 0 : 1;
+    }
+
+    //Set ith Bit
+    public static int setIthBit(int n, int i) {
+        int bitMask = 1<<i;
+        return n | bitMask;
+    }
+
+    //Clear ith Bit
+    public static int clearIthBit(int n, int i) {
+        int bitMask = ~(1<<i);
+        return n & bitMask;
+    }
+
+    //Update ith Bit
+    public static int updateIthBit(int n, int i, int val) {
+        //Method1
+        // if(val == 0) {
+        //     return n & (~(1<<i));
+        // } else {
+        //     return n | (1<<i);
+        // }
+
+        //Method2
+        n = clearIthBit(n, i);
+        int bitMask = val<<i;
+        return n | bitMask;
+    }
+
+    //Clear Last i Bits
+    public static int clearLastIbits(int n, int i) {
+        int bitMask = (~0)<<i; // or (-1)<<i
+        return n | bitMask;
+    }
+
+    //Clear Bits in Range (i,j)
+    public static int clearBitsinRange(int n, int i, int j) {
+        int a = ~0<<i;
+        int b = (1<<i)-1;
+        int bitMask = a | b;
+        return n & bitMask;
+    }
+
+    //Check if number is power of 2 or not
+    public static boolean isPowerof2(int n) {
+        return (n & (n-1)) == 0;
+    }
+
+    //Count number of set bits
+    public static int countSetBits(int n) {
+        int setBits = 0;
+        int bitMask = 1;
+        while(n != 0) {
+            if((n & bitMask) != 0) { //last bit is 1
+                setBits++;
+            }
+            n = n>>1;
+        }
+        return setBits;
+    }
+
+    //a faster method to count set bits
+    public static int countSetBits2(int n) {
+        int setBits = 0;
+        while(n>0) {
+            // removes the last set bit from curr number
+            n = n & (n-1); 
+            setBits++;
+        }
+        return setBits;
+    }
+    public static void main(String args[]) {
+       System.out.println(countSetBits(9));  
+    }
+}

Java/5_Bit Manipulation/BitwiseOperators.java

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+public class BitwiseOperators {
+    public static void main(String args[]) {
+        int a = 0;
+        System.out.println(~a);
+    }
+}

Java/5_Bit Manipulation/FastExponentiation.java

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+public class FastExponentiation {
+    //to calculate a^n
+    public static int pow(int a, int n) {
+        int ans = 1;
+
+        while(n > 0) {
+            if((n&1) != 0) { //checking bit is 0 or 1
+                ans = ans * a;
+            }
+            a = a*a;
+            n = n>>1;
+        }
+
+        return ans;
+    }
+    public static void main(String args[]) {
+        System.out.println(pow(5,3));  
+     }
+}

Java/5_Bit Manipulation/OddEven.java

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+public class OddEven {
+    public static void main(String args[]) {
+        int n = 10;
+        int bitMask = 1;
+        if((n & bitMask) == 0) {
+            System.out.println("even");
+        } else {
+            System.out.println("odd");
+        }
+    }
+}