Utility


1   // $RCSfile: Utility.java,v $
2   //
3   // Project "Principia"
4   //
5   // Michael Meyling
6   // Stoltenstrasse 38
7   // 22119 Hamburg
8   // Germany
9   
10  import java.io.*;
11  
12  
13  /**
14   * A collection of usefull static methods.
15   * @version $Revision: 1.1 $
16   * @author  Michael Meyling
17   */
18  public class Utility {
19  
20  
21     /**
22      * Constructor, should never be called.
23      */
24     private Utility() {
25         super();
26     }
27  
28  
29     /**
30      * Reads a file and returns the contents as a <code>String</code>.
31      *
32      * @param   filename name of the file (could include path)
33      * @return  contents of file
34      * @throws  IOException if a file exception occured
35      */
36     public static final String   loadFile(final String   filename)
37             throws IOException {
38  
39         String   text = null;
40  
41         final File f = new File(filename);
42         final int size = (int) f.length();
43         final FileReader in = new FileReader(filename);
44         final char[] data = new char[size];
45         int charsread = 0;
46         while (charsread < size) {
47             charsread += in.read(data, charsread, size-charsread);
48         }
49         in.close();
50         text = new String  (data);
51         return text;
52     }
53  
54  
55     /**
56      * Reads contents of a file into a string buffer.
57      *
58      * @param   filename    name of the file (could include path)
59      * @param   buffer      buffer to fill with file contents
60      * @throws  IOException if a file exception occured
61      */
62     public static final void loadFile(final String   filename,
63             final StringBuffer   buffer)
64             throws IOException {
65  
66         final File f = new File(filename);
67         final int size = (int) f.length();
68         buffer.setLength(0);
69         final FileReader in = new FileReader(filename);
70         final char[] data = new char[size];
71         int charsread = 0;
72         while (charsread < size) {
73             charsread += in.read(data, charsread, size-charsread);
74         }
75         in.close();
76         buffer.insert(0, data);
77     }
78  
79  
80     /**
81      * Reads contents of a file into a string buffer.
82      *
83      * @param   file        this file will be loaded
84      * @param   buffer      buffer to fill with file contents
85      * @throws  IOException if a file exception occured
86      */
87     public static final void loadFile(final File file,
88             final StringBuffer   buffer)
89             throws IOException {
90  
91         final int size = (int) file.length();
92         buffer.setLength(0);
93         final FileReader in = new FileReader(file);
94         final char[] data = new char[size];
95         int charsread = 0;
96         while (charsread < size) {
97             charsread += in.read(data, charsread, size-charsread);
98         }
99         in.close();
100        buffer.insert(0, data);
101    }
102 
103 
104    /**
105     * Saves a <code>String</code> in a file. In case of an IO error
106     * a message is written to <code>System.out</code>.
107     *
108     * @param   filename    name of the file (could include path)
109     * @param   text        data to save in the file
110     * @throws  IOException if a file exception occured
111     */
112    public static final void saveFile(String   filename, String   text)
113            throws IOException {
114        BufferedWriter out = new BufferedWriter(
115            new FileWriter(filename));
116        out.write(text);
117        out.close();
118    }
119 
120 
121    /**
122     * Saves a <code>String</code> in a file. In case of an IO error
123     * a message is written to <code>System.out</code>.
124     *
125     * @param   filename    name of the file (could include path)
126     * @param   text        data to save in the file
127     * @throws  IOException if a file exception occured
128     */
129    public static final void saveFile(String   filename, StringBuffer   text)
130            throws IOException {
131        BufferedWriter out = new BufferedWriter(
132            new FileWriter(filename));
133        out.write(text.toString());
134        out.close();
135    }
136 
137 
138    /**
139     * Quotes a <code>String</code>. If no quotes exist in the
140     * <code>String</code>, a quote character is appended at the
141     * beginning and the end of the <code>String</code>.
142     *
143     * @param   unquoted    the ungequoted" <code>String</code>
144     * @return  quoted <code>String</code>
145     * @throws  NullPointerException if <code>unquoted == null</code>
146     */
147    public static final String   quote(String   unquoted) {
148 
149        String   result = new String  ("\"");
150 
151        for (int i = 0; i < unquoted.length(); i++) {
152            if (unquoted.charAt(i) == '\"') {
153                result += "\"\"";
154            } else {
155                result += unquoted.charAt(i);
156            }
157        }
158        result += '\"';
159        return result;
160    }
161 
162 
163 
164    /**
165     * Tests if given <code>String</code> begins with a letter and contains
166     * only letters and digits.
167     *
168     * @param   text    test this
169     * @return  is <code>text</code> only made of letters and digits and has
170     *          a leading letter?
171     * @throws  NullPointerException if <code>text == null</code>
172     */
173    public static final boolean isLetterDigitString(final String   text) {
174        if (text.length() <= 0) {
175            return false;
176        }
177        if (!Character.isLetter(text.charAt(0))) {
178            return false;
179        }
180        for (int i = 1; i < text.length(); i++) {
181            if (!Character.isLetterOrDigit(text.charAt(i))) {
182                return false;
183            }
184        }
185        return true;
186    }
187 
188 
189    /**
190     * Replaces all occurences of <code>search</code> in <code>text</code>
191     * by <code>replace</code> and returns the result.
192     *
193     * @param   text    text to work on
194     * @param   search  replace this text by <code>replace</code>
195     * @param   replace replacement for <code>search</code>
196     * @return  resulting string
197     */
198    public final static String   replace(final String   text,
199            final String   search, final String   replace) {
200 
201        final StringBuffer   result = new StringBuffer  ();
202        int pos1 = 0;
203        int pos2;
204        final int len = search.length();
205        while (0 <= (pos2 = text.indexOf(search, pos1))) {
206            result.append(text.substring(pos1, pos2));
207            result.append(replace);
208            pos1 = pos2 + len;
209        }
210        if (pos1 < text.length()) {
211            result.append(text.substring(pos1));
212        }
213        return result.toString();
214    }
215 
216 
217    /**
218     * Waits til a '\n' was read from System.in.
219     */
220    public final static void waitln() {
221        System.out.println("\n..press <return> to continue");
222        try {
223            (new java.io.BufferedReader  (new java.io.InputStreamReader  (
224                System.in))).readLine();
225        } catch (IOException e) {
226        }
227    }
228 
229 
230    /**
231     * Get amount of spaces.
232     *
233     * @param   length  number of spaces
234     * @return  String containig exactly <code>number</code> spaces
235     */
236    public final static StringBuffer   getSpaces(int length) {
237        final StringBuffer   buffer = new StringBuffer  (length);
238        for (int i = 0; i < length; i++) {
239            buffer.append(' ');
240        }
241        return buffer;
242    }
243 
244 
245 }
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