ReadWriteTextFile


1   package org.enhydra.snapper.utils;
2   
3   import java.io.*;
4   
5   public class ReadWriteTextFile {
6       
7   
8     /**
9     * Fetch the entire contents of a text file, and return it in a String.
10    * This style of implementation does not throw Exceptions to the caller.
11    *
12    * @param aFile is a file which already exists and can be read.
13    */
14    static public String   getContents(File aFile) {
15      //...checks on aFile are elided
16      StringBuffer   contents = new StringBuffer  ();
17  
18      //declared here only to make visible to finally clause
19      BufferedReader input = null;
20      try {
21        //use buffering
22        //this implementation reads one line at a time
23        input = new BufferedReader( new FileReader(aFile) );
24        String   line = null; //not declared within while loop
25        while (( line = input.readLine()) != null){
26          contents.append(line);
27          contents.append(System.getProperty("line.separator"));
28        }
29      }
30      catch (FileNotFoundException ex) {
31        ex.printStackTrace();
32      }
33      catch (IOException ex){
34        ex.printStackTrace();
35      }
36      finally {
37        try {
38          if (input!= null) {
39            //flush and close both "input" and its underlying FileReader
40            input.close();
41          }
42        }
43        catch (IOException ex) {
44          ex.printStackTrace();
45        }
46      }
47      return contents.toString();
48    }
49  
50    /**
51    * Change the contents of text file in its entirety, overwriting any
52    * existing text.
53    *
54    * This style of implementation throws all exceptions to the caller.
55    *
56    * @param aFile is an existing file which can be written to.
57    * @throws IllegalArgumentException if param does not comply.
58    * @throws FileNotFoundException if the file does not exist.
59    * @throws IOException if problem encountered during write.
60    */
61    static public void setContents(File aFile, String   aContents)
62                                   throws FileNotFoundException, IOException {
63      if (aFile == null) {
64        throw new IllegalArgumentException  ("File should not be null.");
65      }
66      if (!aFile.exists()) {
67        throw new FileNotFoundException ("File does not exist: " + aFile);
68      }
69      if (!aFile.isFile()) {
70        throw new IllegalArgumentException  ("Should not be a directory: " + aFile);
71      }
72      if (!aFile.canWrite()) {
73        throw new IllegalArgumentException  ("File cannot be written: " + aFile);
74      }
75  
76      //declared here only to make visible to finally clause; generic reference
77      Writer output = null;
78      try {
79        //use buffering
80        output = new BufferedWriter( new FileWriter(aFile) );
81        output.write( aContents );
82      }
83      finally {
84        //flush and close both "output" and its underlying FileWriter
85        if (output != null) output.close();
86      }
87    }
88  
89    public static void main ( String  [] aArguments ) throws IOException {
90      File testFile = new File("C:\\Temp\\blah.txt");
91      setContents(testFile, "blah blah blah");
92  
93      System.out.println( "File contents: " + getContents(testFile) );
94    }
95  }
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