代码有点混乱
不能在讲到一个内容的时候，新建一个包把本节的代码放进里面，这样代码就不会那么混乱了，每个章节都有相应的包相应的代码这样好让学习者更快掌握
4 回答
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
public class IOUtil {
/**
* 单字节读取
* 不适合大文件，读取大文件效率很低
* @param filename
* @throws IOException
*/
public static void printHex(String filename) throws IOException{
FileInputStream in = new FileInputStream(filename);
int b;
int i = 1;
while( (b=in.read())!= -1){
if(b < 0xf){
//单位数前面补0
System.out.print("0");
}
System.out.print(Integer.toHexString(b)+" ");
i++;
if(i%10==0){
System.out.println();
}
}
in.close();
}
/**
* 批量读取字节
* 读取大文件，效率很高，也是最常用的读取文件的方法
* @param filename
* @throws IOException
*/
public static void printHexByByteArray(String filename) throws IOException {
FileInputStream in = new FileInputStream(filename);
byte buf[] = new byte[20*1024];
//从in中批量读取字节，放到buf字节数组中，从第0个位置放，最多放buf.length个，返回的是读到的字节个数
int b = in.read(buf, 0, buf.length);//一次性读完，说明字节数组足够大
int j = 1;
for(int i=0; i<b; i++){
if(buf[i] <= 0xf){
System.out.print(0);
}
System.out.print(Integer.toHexString(buf[i] & 0xff)+" ");//byte只有8位，而int有32位，所以 & 0xff可以清除高位上的数
if(j++%10==0){
System.out.println();
}
}
in.close();
}
public static void copyFileByByte(File src, File dst) throws IOException{
if(!src.exists()){
throw new IllegalArgumentException("文件"+src+"不存在！");
}
if(!src.isFile()){
throw new IllegalArgumentException(src+"不是文件");
}
FileInputStream in = new FileInputStream(src);
FileOutputStream out = new FileOutputStream(dst);
int b = 0;
while((b = in.read()) != -1 ){
out.write(b);
}
in.close();
out.close();
}
/**
* FileOutputStream复制文件
* 用字节数组批量读取文件
* @param src
* @param dst
* @throws IOException
*/
public static void copyFileByByteArray (File src,File dst) throws IOException{
if(!src.exists()){
throw new IllegalArgumentException("文件"+src+"不存在！");
}
if(!src.isFile()){
throw new IllegalArgumentException(src+"不是文件");
}
FileInputStream in = new FileInputStream(src);
/*
* 当dst不存在时，会自动创建，如果存在，删除后在创建
* 如果增加true，则不会删除原文件，会在原文件尾部写出新内容
*/
FileOutputStream out = new FileOutputStream(dst,true);
byte buf[] = new byte[10*1024];
int b = in.read(buf);
out.write(buf, 0, b);
out.flush();
in.close();
out.close();
}
/**
* DataOutputStream
* @throws IOException
*/
public static void dataOutputStream() throws IOException{
String filename = "A/B.txt";
DataOutputStream out = new DataOutputStream(new FileOutputStream(filename));
out.writeInt(6);
out.writeDouble(4.9);
out.writeLong(8l);
out.writeUTF("张基");//以utf-8写入
out.writeChars("张基");//以utf-16be写入
out.close();
}
/**
* DataInputStream
* @throws IOException
*/
public static void dataInputStream() throws IOException{
String filename = "A/B.txt";
DataInputStream in = new DataInputStream(new FileInputStream(filename));
int i = in.readInt();
System.out.println(i);
double j = in.readDouble();
System.out.println(j);
long k = in.readLong();
System.out.println(k);
String str1 = in.readUTF();
System.out.println(str1);
char c = '\0';
while( (c = in.readChar() ) != '\0' ){
System.out.print(c);
}
in.close();
}
/**
* BufferedInputStream , BufferedOutputStream
* 用带缓冲的字节流复制文件
* @param src
* @param dst
* @throws IOException
*/
public static void copyFileByBuffer(File src, File dst) throws IOException{
if(!src.exists()){
throw new IllegalArgumentException("文件"+src+"不存在！");
}
if(!src.isFile()){
throw new IllegalArgumentException(src+"不是文件");
}
BufferedInputStream in = new BufferedInputStream(new FileInputStream(src));
BufferedOutputStream out = new BufferedOutputStream(new FileOutputStream(dst));
int b = 0;
while((b = in.read()) != -1){
out.write(b);
out.flush();//刷新缓冲区
}
in.close();
out.close();
}
/**
* InputStreamReader , OutputStreamWriter
* 处理字符流
* @param filename
* @throws IOException
*/
public static void isrAndOsw(File filename1,File filename2) throws IOException{
InputStreamReader in = new InputStreamReader(new FileInputStream(filename1),"gbk");//项目默认编码
OutputStreamWriter out =new OutputStreamWriter(new FileOutputStream(filename2),"gbk");
/*int b;
while((b=in.read()) != -1){
System.out.print((char)b);
}
*/
char buf[] = new char[8*1024];
int b;
while((b=in.read(buf, 0, buf.length)) != -1){
String s = new String(buf,0,b);
System.out.print(s);
// System.out.println(buf);
// out.write(buf,0,b);
// out.flush();
out.write(s, 0, s.length());
out.flush();
}
in.close();
out.close();
}
/**
* 文件读写流
* @param f1
* @param f2
* @throws IOException
*/
public static void frAndFw(File f1, File f2)throws IOException{
FileReader fr = new FileReader(f1);
FileWriter fw = new FileWriter(f2,true);//如果加上true，则会在f2的末尾追加内容，不会删除原内容
char buf[] = new char[3*1024];
int c = 0;
while(( c = fr.read(buf, 0, buf.length) )!=-1){
fw.write(buf, 0, c);
fw.flush();
}
fw.write("\n");
fw.close();
fr.close();
}
/**
* 字符流过滤器
* @param f1
* @param f2
* @throws IOException
*/
public static void brAnBwFilter(File f1, File f2,File f3) throws IOException{
BufferedReader br = new BufferedReader(
new InputStreamReader(
new FileInputStream(f1)));
BufferedWriter bw = new BufferedWriter(
new OutputStreamWriter(
new FileOutputStream(f2,true)));
// PrintWriter pw = new PrintWriter(f3);
PrintWriter pw = new PrintWriter(
new OutputStreamWriter(
new FileOutputStream(f3,true)));
String line;
while( (line=br.readLine()) != null){//readLine()不能识别原文本中的换行
bw.write(line);
bw.newLine();//手动添加换行
bw.flush();
pw.println(line);
pw.flush();
}
br.close();
bw.close();
pw.close();
}
}import java.io.File;
import java.io.IOException;
public class IOUtil_Test {
public static void main(String[] args) throws IOException {
//IOUtil.printHex("A\\B.txt");
/*
long statime = System.currentTimeMillis();
IOUtil.printHexByByteArray("A\\B.txt");
System.out.println();
long endtime = System.currentTimeMillis();
System.out.println("读取时间:" + (endtime - statime) + "ms" );*/
//IOUtil.copyFileByByteArray(new File("A\\B.txt"), new File("A\\B1.txt"));
/*
IOUtil.dataOutputStream();
IOUtil.printHexByByteArray("A\\B.txt");
System.out.println();
*/
//IOUtil.dataInputStream();
/*
//1
long start1 = System.currentTimeMillis();
IOUtil.copyFileByByte(new File("A\\B1.txt"), new File("A\\bu1.txt"));
long end1 = System.currentTimeMillis();
System.out.println(end1-start1);
//2
long start2 = System.currentTimeMillis();
IOUtil.copyFileByBuffer(new File("A\\B1.txt"), new File("A\\bu2.txt"));
long end2 = System.currentTimeMillis();
System.out.println(end2-start2);
//3
long start3 = System.currentTimeMillis();
IOUtil.copyFileByByteArray(new File("A\\B1.txt"), new File("A\\bu3.txt"));
long end3 = System.currentTimeMillis();
System.out.println(end3-start3);*/
//IOUtil.isrAndOsw(new File("A\\B1.txt"), new File("A\\isAndOsw.txt"));
//IOUtil.frAndFw(new File("A\\B1.txt"), new File("A\\frAndFw.txt"));
IOUtil.brAnBwFilter(new File("A\\B1.txt"), new File("A\\brAnBwFilter.txt"),
new File("A\\brAndBwFilter1.txt"));
}
}上边是所有方法的类，下别是测试类
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