Q5_3.java

package Chapter5;

public class Q5_3{
	public static void main(String[] arg){
		int test1 = 0b001100111001111; // 001100111010111  // 001100110111110
		System.out.println(Integer.toBinaryString(getNext(test1)));
		System.out.println(Integer.toBinaryString(getPrevious(test1)));
		int test2 = 0b001100000111100; // 001100001000111  // 1100000111010
		System.out.println(Integer.toBinaryString(getNext(test2)));
		System.out.println(Integer.toBinaryString(getPrevious(test2)));
	}
	static int getNext(int input){
		int count0 = 0;
		int count1 = 0;
		if(input == 0)
			return 0;
			
		int temp = input;
		while((temp&1) ==0){
			count0++;
			temp = temp >>1;
		}
		while((temp&1) ==1){
			count1++;
			temp = temp>>1;
		}
		// 111111000000  no bigger one31
		// positive number   
		if(count1+count0 == 31)
			return -1;
		temp = temp | 1;
		temp = temp << (count0 +count1);
		int mask = (1<<(count1-1)) -1;
		return mask | temp;
	}
	
	static int getPrevious(int input){
		int temp=input;
		int count0 =0;
		int count1=0;
		if(input == 0)
			return 0;
		while((temp & 1)==1){
			count1++;
			temp = temp >>1;
		}
		while((temp & 1 )==0){
			count0++;			
			temp =temp>>1;
		}
		if(count1+count0==31)
			return -1;
		temp = temp &(~1);
		temp = temp << (count0+count1);		
		int mask = (1<<(count1+1))-1;		
		mask = mask << (count0-1);		
		return mask | temp;
	}
}