java將IP地址轉換爲數字以及逆向轉換（位移和0xFF的使用）

轉載自：

http://www.mkyong.com/java/java-and-0xff-example/

public class BitwiseExample {

	public static void main(String[] args) {

		BitwiseExample obj = new BitwiseExample();
		long ipAddressInLong = obj.ipToLong("192.168.108.108");
		System.out.println(ipAddressInLong);

		String binary = Long.toBinaryString(ipAddressInLong);
		System.out.println(binary);
		printPrettyBinary(binary);

		String ipAddressInString = obj.longToIp(ipAddressInLong);
		System.out.println(ipAddressInString);

	}

	public long ipToLong(String ipAddress) {

		String[] addrArray = ipAddress.split("\\.");

		long num = 0;
		for (int i = 0; i < addrArray.length; i++) {

			int power = 3 - i;

			// 1. (192 % 256) * 256 pow 3
			// 2. (168 % 256) * 256 pow 2
			// 3. (108 % 256) * 256 pow 1
			// 4. (108 % 256) * 256 pow 0
			num += ((Integer.parseInt(addrArray[i]) % 256 * Math
					.pow(256, power)));

		}
		return num;
	}

	public String longToIp(long i) {
		return ((i >> 24) & 0xFF) + "." + ((i >> 16) & 0xFF) + "."
				+ ((i >> 8) & 0xFF) + "." + (i & 0xFF);
	}

	// print pretty binary code, padding left zero
	private static void printPrettyBinary(String binary) {
		String s1 = String.format("%32s", binary).replace(' ', '0');
		System.out.format("%8s %8s %8s %8s %n", s1.substring(0, 8), s1
				.substring(8, 16), s1.substring(16, 24), s1.substring(24, 32));
	}

}

Output:

3232263276
11000000101010000110110001101100
11000000 10101000 01101100 01101100
192.168.108.108

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