public static Integer bytesToInteger(byte[] b){
		
		byte[] a = new byte[4];
		int i = a.length - 1,j = b.length - 1;
		for (; i >= 0 ; i--,j--) {//从b的尾部(即int值的低位)开始copy数据
			if(j >= 0)
				a[i] = b[j];
			else
				a[i] = 0;//如果b.length不足4,则将高位补0
		}
		//&0xff将byte值无差异转成int,避免Java自动类型提升后,会保留高位的符号位
		int v0 = (a[0] & 0xff) << 24;
		int v1 = (a[1] & 0xff) << 16;
		int v2 = (a[2] & 0xff) << 8;
		int v3 = (a[3] & 0xff) ;
		int ret = v0 + v1 + v2 + v3;
		
		//debug 
	    //System.out.println("bytesToInteger:" + ret);
	    //System.out.println("bytesToInteger:" + dump(b));
		return ret;
	}