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  • JVM大端判断

    JVM采用大端方式存多字节的数据,判断方法如下:

     1     public static void bytesToInt() throws IOException {
     2         /**
     3          * 将字节数组(byte[])转为整形(int)
     4          */
     5         byte[] byteAr = new byte[] { 0x78, 0x56, 0x34, 0x12 };
     6         ByteArrayInputStream bais = new ByteArrayInputStream(byteAr);
     7         DataInputStream dis = new DataInputStream(bais);
     8         System.out.println(Integer.toHexString(dis.readInt()));// output: 78563412,说明是大端
     9     }
    10 
    11     public static void intToBytes() throws IOException {
    12         /**
    13          * 将整形(int)转为字节数组(byte[])
    14          */
    15         int a = 0x12345678;
    16         ByteArrayOutputStream baos = new ByteArrayOutputStream();
    17         DataOutputStream dos = new DataOutputStream(baos);
    18         dos.writeInt(a);
    19         byte[] b = baos.toByteArray();
    20         for (int i = 0; i < 4; i++) {
    21             System.out.print(Integer.toHexString(b[i]));
    22         }
    23         System.out.println();// Output: 12345678,说明是大端
    24     }

    采用大小模式对数据进行存放的主要区别在于在存放的字节顺序,大端方式将高位存放在低地址,小端方式将高位存放在高地址。采用大端方式数据存放与阅读顺序一致,符合人类的正常思维,而采用小端方式进行数据存放利于计算机处理。到目前为止,采用大端或者小端进行数据存放,其孰优孰劣也没有定论。

    参考资料:

    Java's Virtual Machine's Endianness-StackOverFlow

    The Java Virtual Machine Specification, Java SE 7 Edition, Chapter 4: The class File Format

    class file consists of a stream of 8-bit bytes. All 16-bit, 32-bit, and 64-bit quantities are constructed by reading in two, four, and eight consecutive 8-bit bytes, respectively. Multibyte data items are always stored in big-endian order, where the high bytes come first. In the Java SE platform, this format is supported by interfaces java.io.DataInput and java.io.DataOutput and classes such as java.io.DataInputStream and java.io.DataOutputStream.

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  • 原文地址:https://www.cnblogs.com/z-sm/p/6049172.html
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