Source Code Cross Referenced for ArrayUtil.java in  » Web-Framework » RSF » uk » org » ponder » arrayutil » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » Web Framework » RSF » uk.org.ponder.arrayutil 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        package uk.org.ponder.arrayutil;
002:
003:        import java.lang.reflect.Array;
004:
005:        import uk.org.ponder.reflect.ClassGetter;
006:        import uk.org.ponder.stringutil.CharWrap;
007:
008:        /**
009:         * This class supplies a selection of useful methods to operate on Java arrays.
010:         * With these methods, arrays can behave very much like Vectors, only with much
011:         * greater time and space efficiency where the length is short or modifications
012:         * are infrequent.
013:         */
014:
015:        public class ArrayUtil {
016:            // TODO: Does the [L syntax also work for primitive types?
017:            private static double[] doubleexemplar = new double[0];
018:            public static Class doubleArrayClass = doubleexemplar.getClass();
019:            private static int[] intexemplar = new int[0];
020:            public static Class intArrayClass = intexemplar.getClass();
021:            public static Class stringArrayClass = ClassGetter
022:                    .forName("[Ljava.lang.String;");
023:
024:            /**
025:             * Concatenates two arrays of the same reference type to return a larger
026:             * array.
027:             * 
028:             * @param array1 The first array to be concatenated.
029:             * @param array2 The second array to be concatenated.
030:             * @return An array whose length is the sum of the lengths of the input
031:             *         arrays, and contains the elements of the second array appended to
032:             *         the elements of the first.
033:             */
034:            public static final Object[] concat(Object[] array1, Object[] array2) {
035:                Class component1 = array1.getClass().getComponentType();
036:                Object[] togo = (Object[]) Array.newInstance(component1,
037:                        array1.length + array2.length);
038:                System.arraycopy(array1, 0, togo, 0, array1.length);
039:                System.arraycopy(array2, 0, togo, array1.length, array2.length);
040:                return togo;
041:            }
042:
043:            /**
044:             * Expands the supplied array by the given factor, to return an array with the
045:             * same contents padded by null.
046:             * 
047:             * @param array1 The array to be expanded.
048:             * @param scalefactor The factor the size of the array is to be enlarged by -
049:             *          clearly this must be a number greater than 1.0.
050:             * @return An array with the required size, with the contents of the supplied
051:             *         array copied into its first portion.
052:             */
053:
054:            public static final Object[] expand(Object[] array1,
055:                    double scalefactor) {
056:                Class component1 = array1.getClass().getComponentType();
057:                Object[] togo = (Object[]) Array.newInstance(component1,
058:                        (int) (array1.length * scalefactor));
059:                System.arraycopy(array1, 0, togo, 0, array1.length);
060:                return togo;
061:            }
062:
063:            /**
064:             * Expands the supplied array to the specified size, to return an array with
065:             * the same contents padded by null.
066:             * 
067:             * @param array1 The array to be expanded.
068:             * @param newsize The required size of the array.
069:             * @return An array with the required size, with the contents of the supplied
070:             *         array copied into its first portion.
071:             */
072:
073:            public static final Object[] expand(Object[] array1, int newsize) {
074:                Class component1 = array1.getClass().getComponentType();
075:                Object[] togo = (Object[]) Array.newInstance(component1,
076:                        newsize);
077:                System.arraycopy(array1, 0, togo, 0, array1.length);
078:                return togo;
079:            }
080:
081:            /**
082:             * Expands the supplied array by the given factor, to return an array with the
083:             * same contents padded by null.
084:             * 
085:             * @param array1 The array to be expanded.
086:             * @param scalefactor The factor the size of the array is to be enlarged by -
087:             *          clearly this must be a number greater than 1.0.
088:             * @return An array with the required size, with the contents of the supplied
089:             *         array copied into its first portion.
090:             */
091:
092:            public static final byte[] expand(byte[] array1, double scalefactor) {
093:                byte[] togo = new byte[(int) (array1.length * scalefactor)];
094:                System.arraycopy(array1, 0, togo, 0, array1.length);
095:                return togo;
096:            }
097:
098:            /**
099:             * Trims the supplied array to the specified size, to return an array with
100:             * only the elements from the first portion of the supplied array.
101:             * 
102:             * @param array1 The array to be trimmed.
103:             * @param tolength The number of elements to be returned from the beginning of
104:             *          the array.
105:             * @return An array containing only the first <code>tolength</code> elements
106:             *         of the supplied array.
107:             */
108:
109:            public static final Object[] trim(Object[] array1, int tolength) {
110:                Class component1 = array1.getClass().getComponentType();
111:                Object[] togo = (Object[]) Array.newInstance(component1,
112:                        tolength);
113:                System.arraycopy(array1, 0, togo, 0, tolength);
114:                return togo;
115:            }
116:
117:            /**
118:             * Returns a sub-array whose elements are copied from a range of the entries
119:             * in the supplied array.
120:             * 
121:             * @param array1 The source array
122:             * @param tolength The number of elements to be returned from the beginning of
123:             *          the array.
124:             * @return An array containing the elements from index <code>start</code>
125:             *         (inclusive) to index <code>end</code> (not inclusive) from the
126:             *         source array.
127:             */
128:
129:            public static final Object[] subArray(Object[] array1, int start,
130:                    int end) {
131:                Class component1 = array1.getClass().getComponentType();
132:                Object[] togo = (Object[]) Array.newInstance(component1, end
133:                        - start);
134:                System.arraycopy(array1, start, togo, 0, end - start);
135:                return togo;
136:            }
137:
138:            /**
139:             * Appends a single object to the end of the supplied array, returning an
140:             * array one element longer than the supplied array.
141:             * 
142:             * @param array1 The array to which the element is to be appended, or
143:             *          <code>null</code> if no array yet exists.
144:             * @param toappend The object to be appended to the array.
145:             * @return A new array one element longer than the supplied array, with the
146:             *         supplied object copied into the final place.
147:             */
148:
149:            public static final Object[] append(Object[] array1, Object toappend) {
150:                Class component1 = array1 == null ? toappend.getClass()
151:                        : array1.getClass().getComponentType();
152:                int length = array1 == null ? 0 : array1.length;
153:                Object[] togo = (Object[]) Array.newInstance(component1,
154:                        length + 1);
155:                if (length > 0) {
156:                    System.arraycopy(array1, 0, togo, 0, array1.length);
157:                }
158:                togo[length] = toappend;
159:                return togo;
160:            }
161:
162:            /**
163:             * Determines whether the supplied array contains a given element. Equality
164:             * will be determined by the <code>.equals()</code> method.
165:             * 
166:             * @param array The array to be searched for the supplied element.
167:             * @param tofind The element to be found in the array.
168:             * @return <code>true</code> if the element was found in the array.
169:             */
170:
171:            public static final boolean contains(Object[] array, Object tofind) {
172:                for (int i = 0; i < array.length; ++i) {
173:                    if (array[i].equals(tofind))
174:                        return true;
175:                }
176:                return false;
177:            }
178:
179:            /**
180:             * Finds the first index that the supplied element appears at in a given
181:             * array. Equality will be determined by the <code>.equals()</code> method.
182:             * 
183:             * @param array The array to be searched for the supplied element.
184:             * @param tofind The object to be searched for.
185:             * @return The first index that the object appears at in the array, or
186:             *         <code>-1</code> if it is not found.
187:             */
188:
189:            public static final int indexOf(Object[] array, Object tofind) {
190:                for (int i = 0; i < array.length; ++i) {
191:                    if (array[i].equals(tofind))
192:                        return i;
193:                }
194:                return -1;
195:            }
196:
197:            /**
198:             * Finds the first index that the supplied element appears at in a given
199:             * array. Equality will be determined by the <code>.equals()</code> method.
200:             * 
201:             * @param array The array to be searched for the supplied element.
202:             * @param tofind The object to be searched for.
203:             * @return The first index that the object appears at in the array, or
204:             *         <code>-1</code> if it is not found.
205:             */
206:
207:            public static final int indexOf(int[] array, int tofind) {
208:                for (int i = 0; i < array.length; ++i) {
209:                    if (array[i] == tofind)
210:                        return i;
211:                }
212:                return -1;
213:            }
214:
215:            /**
216:             * Removes an element from an array, by causing all the elements beyond it to
217:             * shuffle back one place.
218:             * 
219:             * @param array The array from which the element is to be removed.
220:             * @param index The index from which the element is to be removed.
221:             * @return The same array that was input, with the elements past the specified
222:             *         index shuffled back one place.
223:             */
224:
225:            public static final void removeElementAtShift(Object[] array,
226:                    int index) {
227:                System.arraycopy(array, index + 1, array, index, array.length
228:                        - index - 1);
229:            }
230:
231:            public static final Object[] removeElementAt(Object[] array,
232:                    int index) {
233:                Class component1 = array.getClass().getComponentType();
234:                Object[] togo = (Object[]) Array.newInstance(component1,
235:                        array.length - 1);
236:
237:                for (int i = 0; i < index; ++i) {
238:                    togo[i] = array[i];
239:                }
240:                for (int i = index + 1; i < array.length; ++i) {
241:                    togo[i - 1] = array[i];
242:                }
243:
244:                return togo;
245:            }
246:
247:            public static int lexicalCompare(Comparable[] array1, int length1,
248:                    Comparable[] array2, int length2) {
249:                int i = 0;
250:                while (true) {
251:                    if (i >= length1) {
252:                        // off the end of 1 means that 1 is possibly shorter
253:                        if (length1 == length2)
254:                            return 0;
255:                        else
256:                            return -1;
257:                    }
258:                    if (i >= length2)
259:                        return 1;
260:                    Comparable a1 = array1[i];
261:                    Comparable a2 = array2[i];
262:                    if (a1 == null && a2 != null)
263:                        return -1;
264:                    if (a2 != null && a2 == null)
265:                        return 1;
266:                    if (a1 != null && a2 != null) {
267:                        if (a1.compareTo(a2) < 0)
268:                            return -1;
269:                        else if (a1.compareTo(a2) > 0)
270:                            return 1;
271:                    }
272:                    ++i;
273:                }
274:            }
275:
276:            public static boolean equals(String string, char[] buffer,
277:                    int start, int length) {
278:                if (length != string.length())
279:                    return false;
280:                for (int i = length - 1; i >= 0; --i) {
281:                    if (buffer[start + i] != string.charAt(i))
282:                        return false;
283:                }
284:                return true;
285:            }
286:
287:            /**
288:             * Converts the supplied array into a String for debugging purposes.
289:             * 
290:             * @return A String formed from the results of the <code>.toString()</code>
291:             *         method on each array element, separated by single space characters.
292:             *         If the supplied array is null, returns the string <code>null</code>.
293:             */
294:
295:            public static final String toString(Object[] array) {
296:                if (array == null)
297:                    return "null";
298:                CharWrap togo = new CharWrap();
299:                for (int i = 0; i < array.length; ++i) {
300:                    togo
301:                            .append(array[i] == null ? "null" : array[i]
302:                                    .toString());
303:                    if (i != array.length - 1)
304:                        togo.append(' ');
305:                }
306:                return togo.toString();
307:            }
308:
309:        }
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