之前在项目组时,写银行接口时,老是不太明白大端和小端模式会带来什么影响,今儿有空,正好把它给弄明白了。
代码如下,有详细的注释:
package com.io; import java.io.DataOutputStream; import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import java.nio.ByteBuffer; import java.nio.channels.FileChannel; import java.util.Arrays; public class IoOutput { public static void main(String[] args) { /** * 小端模式转化int */ byte[] bytes = intToByteArray1(25105); System.out.println(Arrays.toString(bytes)); System.out.println(new String(bytes)); /** * DataOutputstream.writeint 来写入文件 */ writerFile(); /** * nio 来读入字节 */ readFile(); } /** * nio高性能读取出字节数组 * 经验证,是以小端模式存放于数组 */ public static void readFile(){ try { FileInputStream input = new FileInputStream(new File("test.txt")) ; FileChannel channel = input.getChannel() ; long length = channel.size() ; ByteBuffer byteBuffer = ByteBuffer.allocate((int)length); channel.read(byteBuffer); byteBuffer.flip(); byte[] bytes = byteBuffer.array() ; byteBuffer.clear(); channel.close(); input.close(); int index = 0; int size = bytesHighFirstToInt(bytes, index); index += 4; System.out.println((char)size); //System.out.println(Arrays.toString(bytes)); } catch (FileNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } /** * 将字符“我”转化为整数,写入文件 * 经查,以小端模式写入文件 */ public static void writerFile(){ try { DataOutputStream output = new DataOutputStream(new FileOutputStream("test.txt")); char c = '我' ; int i = c ; output.writeInt(i); output.flush(); output.close(); } catch (FileNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } /** * 按小端转化 * @param i * @return */ public static byte[] intToByteArray1(int i) { byte[] result = new byte[4]; result[0] = (byte) ((i >> 24) & 0xFF); result[1] = (byte) ((i >> 16) & 0xFF); result[2] = (byte) ((i >> 8) & 0xFF); result[3] = (byte) (i & 0xFF); return result; } /** * 字节数组和整型的转换,大端转化,适用于读取writeInt的数据 * * @param bytes 字节数组 * @return 整型 */ public static int bytesHighFirstToInt(byte[] bytes, int start) { int num = bytes[start + 3] & 0xFF; num |= ((bytes[start + 2] << 8) & 0xFF00); num |= ((bytes[start + 1] << 16) & 0xFF0000); num |= ((bytes[start] << 24) & 0xFF000000); return num; } }