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Java > Open Source Codes > javax > measure > units > TransformedUnit


1 /*
2  * JScience - Java(TM) Tools and Libraries for the Advancement of Sciences.
3  * Copyright (C) 2006 - JScience (http://jscience.org/)
4  * All rights reserved.
5  *
6  * Permission to use, copy, modify, and distribute this software is
7  * freely granted, provided that this notice is preserved.
8  */
9 package javax.measure.units;
10
11 import javax.measure.converters.UnitConverter;
12 import javax.measure.quantities.Quantity;
13
14 /**
15  * <p> This class represents the units derived from other units using
16  * {@link UnitConverter converters}.</p>
17  *
18  * <p> Examples of transformed units:[code]
19  * CELSIUS = KELVIN.add(273.15);
20  * FOOT = METER.multiply(0.3048);
21  * MILLISECOND = MILLI(SECOND);
22  * [/code]</p>
23  *
24  * <p> Transformed units have no label. But like any other units,
25  * they may have labels attached to them:[code]
26  * UnitFormat.getStandardInstance().label(FOOT, "ft");
27  * [/code]
28  * or aliases: [code]
29  * UnitFormat.getStandardInstance().alias(CENTI(METER)), "centimeter");
30  * UnitFormat.getStandardInstance().alias(CENTI(METER)), "centimetre");
31  * [/code]</p>
32  *
33  * @author <a HREF="mailto:jean-marie@dautelle.com">Jean-Marie Dautelle</a>
34  * @version 3.1, April 22, 2006
35  * @see Unit#plus(double)
36  * @see Unit#times(double)
37  * @see Unit#transform(UnitConverter)
38  * @see UnitFormat
39  */
40 public final class TransformedUnit<Q extends Quantity> extends DerivedUnit<Q> {
41
42     /**
43      * Holds the parent unit (not a transformed unit).
44      */
45     private final Unit<Q> _parentUnit;
46
47     /**
48      * Holds the converter to the parent unit.
49      */
50     private final UnitConverter _toParentUnit;
51
52     /**
53      * Creates a transformed unit from the specified parent unit.
54      *
55      * @param parentUnit the untransformed unit from which this unit is
56      * derived.
57      * @param toParentUnit the converter to the parent units.
58      * @throws IllegalArgumentException if <code>toParentUnit ==
59      * {@link UnitConverter#IDENTITY UnitConverter.IDENTITY}</code>
60      */
61     TransformedUnit(Unit<Q> parentUnit, UnitConverter toParentUnit) {
62         if (toParentUnit == UnitConverter.IDENTITY)
63             throw new IllegalArgumentException JavaDoc("Identity not allowed");
64         _parentUnit = parentUnit;
65         _toParentUnit = toParentUnit;
66     }
67         
68     /**
69      * Returns the parent unit for this unit. The parent unit is the
70      * untransformed unit from which this unit is derived.
71      *
72      * @return the untransformed unit from which this unit is derived.
73      */
74     public Unit<Q> getParentUnit() {
75         return _parentUnit;
76     }
77         
78     /**
79      * Returns the converter to the parent unit.
80      *
81      * @return the converter to the parent unit.
82      */
83     public UnitConverter toParentUnit() {
84         return _toParentUnit;
85     }
86         
87     /**
88      * Indicates if this transformed unit is considered equals to the specified
89      * object (both are transformed units with equal parent unit and equal
90      * converter to parent unit).
91      *
92      * @param that the object to compare for equality.
93      * @return <code>true</code> if <code>this</code> and <code>that</code>
94      * are considered equals; <code>false</code>otherwise.
95      */
96     public boolean equals(Object JavaDoc that) {
97         if (this == that) return true;
98         if (!(that instanceof TransformedUnit)) return false;
99         TransformedUnit thatUnit = (TransformedUnit) that;
100         return this._parentUnit.equals(thatUnit._parentUnit) &&
101                  this._toParentUnit.equals(thatUnit._toParentUnit);
102     }
103
104     // Implements abstract method.
105 public int hashCode() {
106         return _parentUnit.hashCode() + _toParentUnit.hashCode();
107     }
108
109     // Implements abstract method.
110 public Unit<? super Q> getSystemUnit() {
111         return _parentUnit.getSystemUnit();
112     }
113
114     // Implements abstract method.
115 public UnitConverter toSystemUnit() {
116         return _parentUnit.toSystemUnit().concatenate(_toParentUnit);
117     }
118
119     private static final long serialVersionUID = 1L;
120
121 }
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