Predicates


1   package uk.co.jezuk.mango;
2   
3   /**
4    * The Mango Library Unary and Binary Predicates
5    *
6    * @author Jez Higgins, jez@jezuk.co.uk
7    * @version $Id: Predicates.java 80 2003-04-03 12:44:26Z jez $
8    */
9   public class Predicates
10  {
11    ///////////////////////////////////////////////////////
12    // Unary Predicates
13    /**
14     * A <code>Predicate</code> which always returns <code>true</code>
15     */
16    static public Predicate True() { return new uk.co.jezuk.mango.unarypredicates.True(); }
17    /**
18     * A <code>Predicate</code> which always returns <code>false</code>
19     */
20    static public Predicate False() { return new uk.co.jezuk.mango.unarypredicates.False(); }
21    /**
22     * A <code>Predicate</code> which is the logical negation of some other <code>Predicate</code>.  If <code>n</code>
23     * is a <code>Not</code> object, and <code>pred</code> is the <code>Predicate</code> it was constructed with,
24     * then <code>n.test(x)</code> returns <code>!pred.test(x)</code>.
25     */
26    static public Predicate Not(Predicate pred) { return new uk.co.jezuk.mango.unarypredicates.Not(pred); }
27    /**
28     * A <code>Predicate</code> which returns the logical AND of two other <code>Predicate</code>.  If <code>a</code>
29     * is an <code>And</code> object, constructed with <code>pred1</code> and <code>pred2</code>, then 
30     * <code>a.test(x)</code> returns <code>pred1.test(x) && pred2.test(x)</code>
31     */
32    static public Predicate And(Predicate pred1, Predicate pred2) { return new uk.co.jezuk.mango.unarypredicates.And(pred1, pred2); }
33    /**
34     * A <code>Predicate</code> which returns the logical OR of two other <code>Predicate</code>.  If <code>a</code>
35     * is an <code>Or</code> object, constructed with <code>pred1</code> and <code>pred2</code>, then 
36     * <code>a.test(x)</code> returns <code>pred1.test(x) || pred2.test(x)</code>
37     */
38    static public Predicate Or(Predicate pred1, Predicate pred2) { return new uk.co.jezuk.mango.unarypredicates.Or(pred1, pred2); }
39  
40    /////////////////////////////////////////////////
41    // Binary Predicates
42    /**
43     * <code>BinaryPredicate</code> testing for equality.
44     * <code>true</code> if <code>x.equals(y)</code> or <code>(x == null && y == null)</code>
45     */
46    static public BinaryPredicate EqualTo() { return new uk.co.jezuk.mango.binarypredicates.EqualTo(); }
47    /**
48     * <code>BinaryPredicate</code> that returns true if <code>x</code> is greater than <code>y</code>.
49     * <code>x</code> and <code>y</code> must implement the <code>java.lang.Comparable<code> interface.
50     */
51    static public BinaryPredicate GreaterThan() { return new uk.co.jezuk.mango.binarypredicates.GreaterThan(); }
52    /**
53     * <code>BinaryPredicate</code> that returns true if <code>x</code> is greater than or equal to <code>y</code>.
54     * <code>x</code> and <code>y</code> must implement the <code>java.lang.Comparable<code> interface.
55     */
56    static public BinaryPredicate GreaterThanEquals() { return new uk.co.jezuk.mango.binarypredicates.GreaterThanEquals(); }
57    /**
58     * <code>BinaryPredicate</code> that returns true if <code>x</code> is less than <code>y</code>.
59     * <code>x</code> and <code>y</code> must implement the <code>java.lang.Comparable<code> interface.
60     */
61    static public BinaryPredicate LessThan() { return new uk.co.jezuk.mango.binarypredicates.LessThan(); }
62    /**
63     * <code>BinaryPredicate</code> that returns true if <code>x</code> is less than or equal to <code>y</code>.
64     * <code>x</code> and <code>y</code> must implement the <code>java.lang.Comparable<code> interface.
65     */
66    static public BinaryPredicate LessThanEquals() { return new uk.co.jezuk.mango.binarypredicates.LessThanEquals(); }
67    /**
68     * <code>true</code> if <code>not(x.equals(y))</code>, <code>(x == null) && not(y == null)</code> or <code>not(x == null) && (y == null)</code>
69     */
70    static public BinaryPredicate NotEqualTo() { return new uk.co.jezuk.mango.binarypredicates.NotEqualTo(); }
71    /**
72     * A <code>BinaryPredicate</code> which is the logical negation of some other <code>BinaryPredicate</code>.  If <code>n</code>
73     * is a <code>Not</code> object, and <code>pred</code> is the <code>Predicate</code> it was constructed with,
74     * then <code>n.test(x,y)</code> returns <code>!pred.test(x,y)</code>.
75     */
76    static public BinaryPredicate Not(BinaryPredicate pred) { return new uk.co.jezuk.mango.binarypredicates.Not(pred); }
77    /**
78     * A <code>BinaryPredicate</code> which returns the logical AND of two other <code>BinaryPredicate</code>.  If <code>a</code>
79     * is an <code>And</code> object, constructed with <code>pred1</code> and <code>pred2</code>, then 
80     * <code>a.test(x,y)</code> returns <code>pred1.test(x,y) && pred2.test(x,y)</code>
81     */
82    static public BinaryPredicate And(BinaryPredicate pred1, BinaryPredicate pred2) { return new uk.co.jezuk.mango.binarypredicates.And(pred1, pred2); }
83    /**
84     * A <code>BinaryPredicate</code> which returns the logical OR of two other <code>BinaryPredicate</code>.  If <code>a</code>
85     * is an <code>Or</code> object, constructed with <code>pred1</code> and <code>pred2</code>, then 
86     * <code>a.test(x,y)</code> returns <code>pred1.test(x,y) || pred2.test(x,y)</code>
87     */
88    static public BinaryPredicate Or(BinaryPredicate pred1, BinaryPredicate pred2) { return new uk.co.jezuk.mango.binarypredicates.Or(pred1, pred2); }
89  
90    //////////////////////////////////
91    private Predicates() { }
92  } // Predicates
93  
94  
95
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