private String generateCoinbase(String en2){
    StringBuilder coinbase = new StringBuilder();
    coinbase.append(coinb1);
    coinbase.append(Extranonce1);
    coinbase.append(en2);
    coinbase.append(coinb2);
    return coinbase.toString();
}

public String Merkle2(String cb) {
    String mr = cb;
    for(int i = 0; i < merkle_branch.length; ++i)
        mr = sha256(sha256(mr + merkle_branch[i]));
    return mr;
}

public String reverse(String string) {
    int n = string.length() / 2;
    StringBuilder sb = new StringBuilder();
    for(int i = (n - 1) * 2; n >= 0; n-=2)
        sb.append(string.substring(i, i + 1));
    return sb.toString();
}

public String reverse8(String string) {
    StringBuilder sb = new StringBuilder();
    for(int i = 0; i < string.length(); i+=8){
        int end = Math.min(i + 7, string.length() - 1);
        sb.append(reverse(string.substring(i, end)));
    }
    return sb.toString();
}

public String testControll(String nonce2, String en2) {
    String coinbase = sha256(sha256(generateCoinbase(en2)));
    String merkle = Merkle2(coinbase);
    String header = version + prevhash + reverse8(merkle) + ntime +
            nbits + nonce2 + "000000800000000000000000000000000000000000000000000000000000000000000000000000000000000080020000";
    String hash = sha256(sha256(header));
    return hash;
}