java（I/O）檔案讀寫

上面我們講了Hello World!，我們完成了一個程式，得到的結果該如何儲存，總不能每次開機都要運作一次吧？是以我們需要一個載體把我們的結果記錄下來。下面我就介紹一個友善的記錄方式，檔案讀寫。

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.RandomAccessFile;

public class TestFile {
	
	 public TestFile(){
		 
		 
	 }
	
	 
	 
	 public void appendWriterFile(String fileName,String content){	 
		 try {
			FileWriter writer = new FileWriter(fileName,true);
			writer.write(content);
			writer.close();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		 
	 }
	 
	 public void writerFile(String fileName,String content){
				 
		 try {
			FileWriter writer = new FileWriter(fileName);
			writer.write(content);
			writer.close();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		 
	 }
	 

	 public String readFile(String fileName){
		 StringBuffer results = new StringBuffer();
		 File file = new File(fileName);  
		 BufferedReader reader = null;
	     try {
			reader = new BufferedReader(new FileReader(file));
			String tempString = null;
			 while ((tempString = reader.readLine()) != null) { 
				 results.append(tempString+"\r\n");
			 }
			 reader.close();
			
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}finally {  
            if (reader != null) {  
                try {  
                    reader.close();  
                } catch (IOException e1) {  
                }  
            }  
        }
		return results.toString();    
         	 
	 }
	 
	 public void randomWriterFile(String fileName,String content){
		 
		 try {
			RandomAccessFile writer = new RandomAccessFile(fileName, "rw"); 
			long length = writer.length();
			writer.seek(length);
			writer.writeBytes(content);
			writer.close();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		 
	 }
	 
	 public String randomReadFile(String fileName){
		 StringBuffer results = new StringBuffer();
		 RandomAccessFile reader = null; 
	     try {
			reader = new RandomAccessFile(fileName, "r"); 
			long length = reader.length();  
            // 讀檔案的起始位置  
            int index = (length > 4) ? 4 : 0;  
            // 将讀檔案的開始位置移到beginIndex位置。  
            reader.seek(index);  
			String tempString = null;
			 while ((tempString = reader.readLine()) != null) { 
				 results.append(tempString+"\r\n");
			 }
			 reader.close();
			
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}finally {  
            if (reader != null) {  
                try {  
                    reader.close();  
                } catch (IOException e1) {  
                }  
            }  
        }
		return results.toString();    
         	 
	 }
	
	 public static void main(String[] args) { 
		 String fileName="/Users/victor/test.txt";
		 String content="Hello World!\r\n";   // 加入換行符 \r\n
		 
		 TestFile test =new TestFile();
		 //寫入檔案
		 test.writerFile(fileName, content);
		 test.appendWriterFile(fileName, content);  //追加寫入
		 //讀取檔案
		 String results = test.readFile(fileName);
		 System.out.println(results);		  
		 
	 }

}
           

快速的學會檔案的讀寫，這些能滿足大家大部分需求，如果要對流操作請查api。

文章引用 2dot5