java byte[]转int和double

一般无需java来处理byte字节的数据转成 int , C语言更适合干这事. 但是无奈遇到了这种需求.

网上百度了一小部分代码, 发现好多错误代码… 干脆自己手写了一遍…

byte[]数据的格式协议文档如下:

先上使用代码

byte[] hex = Base64.getDecoder().decode(data);
int head = Read3Bytes(hex, 0) ;// 3个字节  1b7273
 if(head !=  1798771) // 十进制 1798771 ==== 16进制 0x1b7273
 {
  throw new Exception("不可识别的数据包");
 }
// 数据长度是  
int datalength =  Read1Bytes(hex, 3); //1字节 此数据后面所带的有效数据长度
// 命令字
int cmd = Read1Bytes(hex, 4); ; // 命令字 0：服务器通过get获取  1：开门   2：关门
//温度
int wendu = Read3Bytes(hex, 5) ;// 3个字节  0x01+2字节温度数据 
//湿度
int shidu = Read2Bytes(hex, 8);// 2个字节  2字节湿度数据
//距离：            0x02+2字节距离数据
int juli =   Read3Bytes(hex, 10);

下面是主要代码

//循环累加、或运算都可以
    public static int Read1Bytes(byte[] bytes,int startindex){
        return  bytes[startindex]  ;  
    }
    
    public static int Read2Bytes(byte[] bytes,int startindex){
        return   bytes[startindex] << 8 
                 | (bytes[startindex + 1] << 0)  ; 


    }
    public static int Read3Bytes(byte[] bytes,int startindex){
        return   bytes[startindex] << 16 
                | (bytes[startindex + 1] <<8) 
                | (bytes[startindex + 2] <<0); 
         
    }
    public static int Read4Bytes(byte[] bytes,int startindex){
        return   bytes[startindex] << 24 
                | (bytes[startindex + 1] << 16) 
                | (bytes[startindex + 2] << 8)
                | (bytes[startindex + 3] << 0); 
        
    }

    public static double Read5Bytes(byte[] bytes,int startindex){
        return    bytes[startindex] << 32 
                | (bytes[startindex + 1] << 24) 
                | (bytes[startindex + 2] << 16)
                | (bytes[startindex + 3] << 8) 
                | (bytes[startindex + 4] << 0); 
        
    }

    public static double Read6Bytes(byte[] bytes,int startindex){
        return    bytes[startindex] << 40 
                | (bytes[startindex + 1] << 32) 
                | (bytes[startindex + 2] << 24)
                | (bytes[startindex + 3] << 16) 
                | (bytes[startindex + 4] << 8)
                | (bytes[startindex + 5] << 0); 
        
    }
    
    public static double Read7Bytes(byte[] bytes,int startindex){
        return   bytes[startindex]  << 48
                | (bytes[startindex + 1] << 40) 
                | (bytes[startindex + 2] << 32) 
                | (bytes[startindex + 3] << 24)
                | (bytes[startindex + 4] << 16) 
                | (bytes[startindex + 5] << 8)
                | (bytes[startindex + 6] << 0); 
        
    }

    public static double Read8Bytes(byte[] bytes,int startindex){
        return    bytes[startindex] << 56 
                | (bytes[startindex + 1] << 48) 
                | (bytes[startindex + 2] << 40) 
                | (bytes[startindex + 3] << 32) 
                | (bytes[startindex + 4] << 24)
                | (bytes[startindex + 5] << 16) 
                | (bytes[startindex + 6] << 8)
                | (bytes[startindex + 7] << 0); 
        
    }