加密算法 -- SHA-256

java的 SHA-256加密，几乎与 MD5加密的写法一样：

import java.security.MessageDigest;
import java.util.Arrays;


public class Hello {
    public static void main(String[] args) {
        String name = "哈喽啊";
        try {
            MessageDigest instance = MessageDigest.getInstance("SHA-256");
            // md5的加盐
            instance.update("xxx".getBytes());
            // md5加密的字节数组
            byte[] nameBytes = instance.digest(name.getBytes());
            System.out.println(Arrays.toString(nameBytes));// 打印结果：[-16, 34, -105, -18, -53, -91, 98, 48, -40, 115, 11, 25, 22, 7, -108, 5, 24, 51, -38, 36, 17, 94, -3, -102, -6, -76, -61, -77, -29, 4, 107, 84]

            String res = new String(nameBytes);
            System.out.println(res);

            //创建一个可变字符串 sb
            StringBuilder sb = new StringBuilder();
            for (int i=0;i<nameBytes.length;i++){
                int val = nameBytes[i] & 255; //将负数转换成整数
                if (val < 16) {
                    sb.append("0");
                }
                // 将val转换成16进制，再添加到sb这个可变的字符串中
                sb.append(Integer.toHexString(val));
            }
            //再将可变的字符串sb ,转换成不可变的字符串
            String hexData = sb.toString();
            System.out.println(hexData); // 打印结果：f02297eecba56230d8730b19160794051833da24115efd9afab4c3b3e3046b54

        }catch (Exception e){
            System.out.println(e);
        }
    }
}