Code Snippet 2: This time in Java

:: CodeCritic, Programming Languages

By: John Clements

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
/**************************************************************
 * 
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 * 
 *   http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 * 
 *************************************************************/



package org.openoffice.xmerge.merger;

/**
 *  This is an interface used by the {@link
 *  org.openoffice.xmerge.merger.DiffAlgorithm
 *  DiffAlgorithm} and {@link
 *  org.openoffice.xmerge.merger.MergeAlgorithm
 *  MergeAlgorithm} to access a <code>Document</code>.
 *
 *  @author smak
 */
public interface Iterator {


    /**
     *  Move to next element in the sequence.
     *
     *  @return  The <code>Object</code> of the next element in the sequence.
     *           If there is no next element, then return null.
     */
    public Object next();


    /**
     *  Move to previous element in the sequence.
     *
     *  @return  The <code>Object</code> of the previous element in the sequence.
     *           If there is no previous element, then return null.
     */
    public Object previous();


    /**
     * Move to the beginning of the sequence.
     *
     * @return  The <code>Object</code> of the first element in the sequence.
     *          If it is empty, then return null.
     */
    public Object start();


    /**
     * Move to the end of the sequence.
     *
     * @return  The <code>Object</code> of the last element in the sequence.
     *          If it is empty, then return null.
     */
    public Object end();


    /**
     * Return the current element <code>Object</code> content.
     *
     * @return  The <code>Object</code> at current position.
     */
    public Object currentElement();


    /**
     * Return the total element count in the sequence.
     *
     * @return  The total element count.
     */
    public int elementCount();


    /**
     *  A method to allow the difference algorithm to test whether the
     *  <code>obj1</code> and <code>obj2</code> in the
     *  <code>Iterator</code> are considered equal.  As not every
     *  <code>Object</code> in the <code>Iterator</code> can implement its
     *  own equal method, with this equivalent method, we can allow
     *  flexibility for the <code>Iterator</code> to choose a custom way
     *  to compare two objects.  Two objects can even be compared based on
     *  the position in the <code>Iterator</code> rather than by 
     *  the content via this option.
     *
     *  @param  obj1  The first <code>Object</code>.
     *  @param  obj2  The second <code>Object</code>.
     *
     *  @return  true if equal, false otherwise.
     */
    public boolean equivalent(Object obj1, Object obj2);


    /**
     *  <p>A method to force the <code>Iterator</code> to transverse the tree
     *  again to refresh the content.</p>
     *
     *  <p>It is used mainly for <code>Iterator</code> objects which take a snap
     *  shot instead of dynamically transversing the tree.  The current
     *  position will be set to the beginning.</p>
     */
    public void refresh();
}

Here’s another one, randomly chosen from the source for Apache OpenOffice’s 800K lines of Java (I should point out that there are something like 10M lines of C++ in the project).

A few seconds makes it clear that this is … the iterator interface. Minus the horrible “remove” call, and plus a bunch of other ones, generally fairly inoffensive.

Honestly, I can’t say too many bad things about this file: it’s clear and useful; this is the kind of file you’d like to see when you go looking for information. I had hoped for something more… complex? But the random number generator does what it wants. Darn random number generator!

One point here is that I probably shouldn’t have excluded .h files from my random C file excerpt; in Java, interface files aren’t distinguished from “source” files in the same way they are in C.