package com.snailclimb.ks.securityAlgorithm;

import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class SHA1Demo {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		System.out.println(getSha1("你若安好，便是晴天"));
	
	}

	public static String getSha1(String str) {
		if (null == str || 0 == str.length()) {
			return null;
		}
		char[] hexDigits = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
		try {
			//创建SHA1算法消息摘要对象
			MessageDigest mdTemp = MessageDigest.getInstance("SHA1");
			//使用指定的字节数组更新摘要。
			mdTemp.update(str.getBytes("UTF-8"));
			//生成的哈希值的字节数组
			byte[] md = mdTemp.digest();
			//SHA1算法生成信息摘要关键过程
			int j = md.length;
		    char[] buf = new char[j * 2];
			int k = 0;
			for (int i = 0; i < j; i++) {
				byte byte0 = md[i];
				buf[k++] = hexDigits[byte0 >>> 4 & 0xf];
				buf[k++] = hexDigits[byte0 & 0xf];
			}
			return new String(buf);
		} catch (NoSuchAlgorithmException e) {
			e.printStackTrace();
		} catch (UnsupportedEncodingException e) {
			e.printStackTrace();
		}
		return "0";
		
	}
}