java文件读写操作大全

爱被打了一巴掌 2022-06-08 06:55 155阅读 0赞

**一.获得控制台用户输入的信息**  
  
    public String getInputMessage() throws IOException...\{  
        System.out.println("请输入您的命令∶");  
        byte buffer\[\]=new byte\[1024\];  
        int count=System.in.read(buffer);  
        char\[\] ch=new char\[count-2\];//最后两位为结束符，删去不要  
        for(int i=0;i<count-2;i++)  
            ch\[i\]=(char)buffer\[i\];  
        String str=new String(ch);  
        return str;  
    \}  
    可以返回用户输入的信息，不足之处在于不支持中文输入，有待进一步改进。

**    二.复制文件**  
    1.以文件流的方式复制文件  
  
    public void copyFile(String src,String dest) throwsIOException...\{  
        FileInputStream in=new FileInputStream(src);  
        File file=new File(dest);  
        if(!file.exists())  
            file.createNewFile();  
        FileOutputStream out=new FileOutputStream(file);  
        int c;  
        byte buffer\[\]=new byte\[1024\];  
        while((c=in.read(buffer))!=-1)...\{  
            for(int i=0;i<c;i++)  
                out.write(buffer\[i\]);          
        \}  
        in.close();  
        out.close();  
    \}  
    该方法经过测试，支持中文处理，并且可以复制多种类型，比如txt，xml，jpg，doc等多种格式

**    三.写文件**

1.利用PrintStream写文件

public void PrintStreamDemo()...\{  
        try ...\{  
            FileOutputStream out=new FileOutputStream("D:/test.txt");  
            PrintStream p=new PrintStream(out);  
            for(int i=0;i<10;i++)  
                p.println("This is "+i+" line");  
        \} catch (FileNotFoundException e) ...\{  
            e.printStackTrace();  
        \}  
    \}  
    2.利用StringBuffer写文件  
public void StringBufferDemo() throws IOException......\{  
        File file=new File("/root/sms.log");  
        if(!file.exists())  
            file.createNewFile();  
        FileOutputStream out=newFileOutputStream(file,true);          
        for(int i=0;i<10000;i++)......\{  
            StringBuffer sb=new StringBuffer();  
            sb.append("这是第"+i+"行:前面介绍的各种方法都不关用,为什么总是奇怪的问题 ");  
            out.write(sb.toString().getBytes("utf-8"));  
        \}          
        out.close();  
    \}  
    该方法可以设定使用何种编码，有效解决中文问题。  
**四.文件重命名**  
      
    public void renameFile(String path,String oldname,Stringnewname)...\{  
        if(!oldname.equals(newname))...\{//新的文件名和以前文件名不同时,才有必要进行重命名  
            File oldfile=new File(path+"/"+oldname);  
            File newfile=new File(path+"/"+newname);  
            if(newfile.exists())//若在该目录下已经有一个文件和新文件名相同，则不允许重命名  
                System.out.println(newname+"已经存在！");  
            else...\{  
                oldfile.renameTo(newfile);  
            \}  
        \}           
    \}

**五.转移文件目录**  
    转移文件目录不等同于复制文件，复制文件是复制后两个目录都存在该文件，而转移文件目录则是转移后，只有新目录中存在该文件。  
      
    public void changeDirectory(String filename,String oldpath,Stringnewpath,boolean cover)...\{  
        if(!oldpath.equals(newpath))...\{  
            File oldfile=new File(oldpath+"/"+filename);  
            File newfile=new File(newpath+"/"+filename);  
            if(newfile.exists())...\{//若在待转移目录下，已经存在待转移文件  
                if(cover)//覆盖  
                    oldfile.renameTo(newfile);  
                else  
                    System.out.println("在新目录下已经存在："+filename);  
            \}  
            else...\{  
                oldfile.renameTo(newfile);  
            \}  
        \}         
    \}  
**    六.读文件  
    1.利用FileInputStream读取文件**  
      
    public String FileInputStreamDemo(String path) throwsIOException...\{  
        File file=new File(path);  
        if(!file.exists()||file.isDirectory())  
            throw new FileNotFoundException();  
        FileInputStream fis=new FileInputStream(file);  
        byte\[\] buf = new byte\[1024\];  
        StringBuffer sb=new StringBuffer();  
        while((fis.read(buf))!=-1)...\{  
            sb.append(newString(buf));      
            buf=new byte\[1024\];//重新生成，避免和上次读取的数据重复  
        \}  
        return sb.toString();  
    \}  
**2.利用BufferedReader读取**

在IO操作，利用BufferedReader和BufferedWriter效率会更高一点

public String BufferedReaderDemo(String path) throwsIOException...\{  
        File file=new File(path);  
        if(!file.exists()||file.isDirectory())  
            throw new FileNotFoundException();  
        BufferedReader br=new BufferedReader(new FileReader(file));  
        String temp=null;  
        StringBuffer sb=new StringBuffer();  
        temp=br.readLine();  
        while(temp!=null)...\{  
            sb.append(temp+" ");  
            temp=br.readLine();  
        \}  
        return sb.toString();  
    \}

**  3.利用dom4j读取xml文件**

public Document readXml(String path) throws DocumentException,IOException...\{  
        File file=new File(path);  
        BufferedReader bufferedreader = new BufferedReader(newFileReader(file));  
        SAXReader saxreader = new SAXReader();  
        Document document = (Document)saxreader.read(bufferedreader);  
        bufferedreader.close();  
        return document;  
    \}  
    七.创建文件(文件夹)

**1.创建文件夹    
    public void createDir(String path)...\{  
        File dir=new File(path);  
        if(!dir.exists())  
            dir.mkdir();  
    \}**  
2.创建新文件  
    public void createFile(String path,String filename) throwsIOException...\{  
        File file=new File(path+"/"+filename);  
        if(!file.exists())  
            file.createNewFile();  
    \}  
**    八.删除文件(目录)  
1.删除文件       
    public void delFile(String path,String filename)...\{  
        File file=new File(path+"/"+filename);  
        if(file.exists()&&file.isFile())  
            file.delete();  
    \}**  
2.删除目录  
要利用File类的delete()方法删除目录时，必须保证该目录下没有文件或者子目录，否则删除失败，因此在实际应用中，我们要删除目录，必须利用递归删除该目录下的所有子目录和文件，然后再删除该目录。    
    public void delDir(String path)...\{  
        File dir=new File(path);  
        if(dir.exists())...\{  
            File\[\] tmp=dir.listFiles();  
            for(int i=0;i<tmp.length;i++)...\{  
                if(tmp\[i\].isDirectory())...\{  
                    delDir(path+"/"+tmp\[i\].getName());  
                \}  
                else...\{  
                    tmp\[i\].delete();  
                \}  
            \}  
            dir.delete();  
        \}  
    \}