int num = 40000;

byte first = num/256;

byte second = num%256;

˜q™æ ·åQŒåªè¦?/span>firstæˆ?/span>second­‘…过127åQŒå°±ä¼šæº¢å‡ºï¼Œä»Žè€Œåˆòq¶è“v来的intæ•°å€ég¼šå’ŒåŽŸæ•°å€ég¸ä¸€è‡´ã€?/span>

int input2 = 130;

byte a3 = (byte) input2;

input2 = a3;

System.out.println(input2);

对于上述代码åQŒç»“æžœäØ“-126åQŒè€Œä¸æ˜¯å¼€å§‹çš„130åQŒä¹Ÿæ˜¯æº¢å‡ºçš„问题åQŒæ‰€ä»¥ä¸€å®šè¦æ³¨æ„ã€?/span>

解决æ–ÒŽ³•åQ?/span>

½W¬ä¸€¿Uï¼šè¾ƒäؓ不彻底，对于正整数来è¯ß_¼Œå¯ä»¥é™¤ä»¥127åQŒä»Žè€Œä‹Ébyte不会溢出

½W¬äºŒ¿Uï¼šè½¬åŒ–的时候按位操作，从而不使用强制转化损失¾_‘Öº¦åQ?/span>

// ž®?/span>iSource转äؓ长度ä¸?/span>iArrayLençš?/span>byte数组åQŒå­—节数¾l„的低位是整型的低字节位

public static byte[] toByteArray(int iSource, int iArrayLen)

 {

         byte[] bLocalArr = new byte[iArrayLen];

         for ( int i = 0; (i < 4) && (i < iArrayLen); i++)

         {

                   bLocalArr[i] = (byte)( iSource>>8*i & 0xFF );

         }

         return bLocalArr;

}  

// ž®?/span>byte数组bRefArr转äؓ一个整æ•?/span>,字节数组的低位是整型的低字节ä½?/span>

public static int toInt(byte[] bRefArr)

 {

         int iOutcome = 0;

         byte bLoop;

         for ( int i =0; i<4 ; i++)

         {

                   bLoop = bRefArr[i];

                   iOutcome+= (bLoop & 0xFF) << (8 * i);

         }

         return iOutcome;

}