java读取文件

1、字节形式读取

 1 @Test
 2 public void test1(){
 3     String path = "d://temp/test.txt";
 4     readFile(path);
 5 }
 6 
 7 private void readFile(String path) {
 8     //FileInputStream 用于读取诸如图像数据之类的原始字节流。要读取字符流，请考虑使用 FileReader
 9     File file = new File(path);
10     InputStream in = null;
11     try {
12         in = new FileInputStream(file);
13         int tempStr = 0;
14         while((tempStr = in.read())!=-1){
15             System.out.write(tempStr);
16         }
17     } catch (FileNotFoundException e) {
18         // TODO Auto-generated catch block
19         e.printStackTrace();
20     } catch (IOException e) {
21         // TODO Auto-generated catch block
22         e.printStackTrace();
23     } 
24 }

改进方式一次读取多个字节

 1 private void readFile(String path) {
 2     //FileInputStream 用于读取诸如图像数据之类的原始字节流。要读取字符流，请考虑使用 FileReader
 3     File file = new File(path);
 4     InputStream in = null;
 5     try {
 6         in = new FileInputStream(file);
 7         byte[] byteArr = new byte[1024];
 8         while(in.read(byteArr)!=-1){
 9             System.out.write(byteArr);
10         }
11     } catch (FileNotFoundException e) {
12         // TODO Auto-generated catch block
13         e.printStackTrace();
14     } catch (IOException e) {
15         // TODO Auto-generated catch block
16         e.printStackTrace();
17     } 
18 }

2、字符形式读取

 1 private void readFile(String path) {
 2     File file = new File(path);
 3     InputStreamReader in = null;
 4     try {
 5         in = new InputStreamReader(new FileInputStream(file));
 6         int tempStr;
 7         while((tempStr=in.read())!=-1){
 8             System.out.write(tempStr);
 9         }
10     } catch (FileNotFoundException e) {
11         // TODO Auto-generated catch block
12         e.printStackTrace();
13     } catch (IOException e) {
14         // TODO Auto-generated catch block
15         e.printStackTrace();
16     } finally {
17         if(in!=null)
18             try {
19                 in.close();
20             } catch (IOException e) {
21                 // TODO Auto-generated catch block
22                 e.printStackTrace();
23             }
24     }
25 }

改进方式

 1 private void readFile(String path) {
 2     File file = new File(path);
 3     InputStreamReader in = null;
 4     try {
 5         in = new InputStreamReader(new FileInputStream(file));
 6         char[] charArr = new char[1024];
 7         while(in.read(charArr)!=-1){
 8             System.out.print(charArr);
 9         }
10     } catch (FileNotFoundException e) {
11         // TODO Auto-generated catch block
12         e.printStackTrace();
13     } catch (IOException e) {
14         // TODO Auto-generated catch block
15         e.printStackTrace();
16     } finally {
17         if(in!=null)
18             try {
19                 in.close();
20             } catch (IOException e) {
21                 // TODO Auto-generated catch block
22                 e.printStackTrace();
23             }
24     }
25 }

3、以行为单位读取文件，常用于读面向行的格式化文件，如csv等

 1 private void readFile(String path) {
 2     File file = new File(path);
 3     BufferedReader in = null;
 4     try {
 5         in = new BufferedReader(new FileReader(file));
 6         String tempStr = "";
 7         while((tempStr=in.readLine()) != null){
 8             System.out.println(tempStr);
 9         }
10     } catch (FileNotFoundException e) {
11         // TODO Auto-generated catch block
12         e.printStackTrace();
13     } catch (IOException e) {
14         // TODO Auto-generated catch block
15         e.printStackTrace();
16     } finally {
17         if(in!=null)
18             try {
19                 in.close();
20             } catch (IOException e) {
21                 // TODO Auto-generated catch block
22                 e.printStackTrace();
23             }
24     }
25 }