first commit

Semester 1/Programming 1/Java/examples/file-reader/FileReader.java

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+import java.io.*;
+import java.net.URL;
+
+/**
+ * This is a little demo showing how to read text files. It will find files
+ * that are situated anywhere in the classpath.
+ *
+ * Currently, two demo methods are available. Both simply print a text file to the
+ * terminal. One returns exceptions in case of a problem, the other prints out
+ * error messages.
+ * 
+ * @author Michael K<>lling
+ * @version 1.0 (19. Feb 2002)
+ */
+public class FileReader
+{
+    /**
+     * Create a file reader
+     */
+    public FileReader()
+    {
+        // nothing to do...
+    }
+
+    /**
+     * Show the contents of the file 'fileName' on standard out (the text terminal).
+     *
+     * @param fileName  The name of the file to show
+     * @throws  IOException if the file could not be opened
+     */
+    public void showFile(String fileName)
+        throws IOException
+    {
+        InputStream fstream = openFile(fileName);
+
+        // wrap the stream into an InputStreamReader, so that we read characters
+        // rather than bytes (important for non-ascii characters); then wrap it into
+        // a BufferedReader, so that we can read lines, rather than single characters
+
+        BufferedReader in = new BufferedReader(new InputStreamReader(fstream));
+
+        // okay, we're ready to go...
+
+        System.out.println("File: " + fileName);
+        String line = in.readLine();
+        while(line != null) {
+            System.out.println(line);
+            line = in.readLine();
+        }
+        System.out.println("<end of file>");
+    }
+        
+    /**
+     * Same as 'showfile', but don't throw exceptions. If an error occurs,
+     * write an error message to the terminal.
+     *
+     * @param fileName  The name of the file to show
+     */
+    public void checkedShowFile(String fileName)
+    {
+        try {
+            showFile(fileName);
+        }
+        catch(IOException exc) {
+            System.out.println("There was a problem showing this file.");
+            System.out.println("The error encountered is:");
+            System.out.println(exc);
+        }
+    }
+
+    /**
+     * Open a text file and return a stream to read from that file.
+     * The file can reside anywhere in the classpath.
+     *
+     * @param fileName  The name of the file to open
+     * @return An open stream to read from the file
+     * @throws  IOException if the file could not be opened
+     */
+    public InputStream openFile(String fileName)
+        throws IOException
+    {
+        if(fileName == null)
+            throw new IOException("Cannot open file - filename was null.");
+        URL url = getClass().getClassLoader().getResource(fileName);
+        if(url == null)
+            throw new IOException("File not found: " + fileName);
+        return url.openStream();
+    }
+}