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Java > Open Source Codes > gnu > math > NamedUnit


1 // Copyright (c) 2000 Per M.A. Bothner.
2 // This is free software; for terms and warranty disclaimer see ./COPYING.
3
4 package gnu.math;
5 import java.io.*;
6
7 /** A Unit that has a name. */
8
9 public class NamedUnit extends Unit implements Externalizable
10 {
11   /** The interned name of this Unit, for example "cm". */
12   String JavaDoc name;
13
14   /** The value of this Unit is scale*base.
15    * The value of this.factor is scale*base.factor, so scale is
16    * redundant - were it not for rounding error concerns. */
17   double scale;
18
19   /** The value this was initialized from. */
20   Unit base;
21
22   /** Next NamedUnit in table bucket. */
23   NamedUnit chain;
24
25   public NamedUnit ()
26   {
27   }
28
29   public NamedUnit (String JavaDoc name, DQuantity value)
30   {
31     this.name = name.intern();
32     scale = value.factor;
33     base = value.unt;
34     init();
35   }
36
37   public NamedUnit (String JavaDoc name, double factor, Unit base)
38   {
39     this.name = name;
40     this.base = base;
41     scale = factor;
42     init();
43   }
44
45   protected void init ()
46   {
47     factor = scale * base.factor;
48     dims = base.dims;
49     name = name.intern();
50     int hash = name.hashCode();
51     int index = (hash & 0x7FFFFFFF) % table.length;
52     chain = table[index];
53     table[index] = this;
54   }
55
56   public String JavaDoc getName() { return name; }
57
58   public static NamedUnit lookup (String JavaDoc name)
59   {
60     name = name.intern();
61     int hash = name.hashCode();
62     int index = (hash & 0x7FFFFFFF) % table.length;
63     for (NamedUnit unit = table[index]; unit != null; unit = unit.chain)
64       {
65     if (unit.name == name)
66       return unit;
67       }
68     return null;
69   }
70
71   public static NamedUnit lookup (String JavaDoc name, double scale, Unit base)
72   {
73     name = name.intern();
74     int hash = name.hashCode();
75     int index = (hash & 0x7FFFFFFF) % table.length;
76     for (NamedUnit unit = table[index]; unit != null; unit = unit.chain)
77       {
78     if (unit.name == name && unit.scale == scale && unit.base == base)
79       return unit;
80       }
81     return null;
82   }
83
84   public static NamedUnit make (String JavaDoc name, double scale, Unit base)
85   {
86     NamedUnit old = lookup(name, scale, base);
87     return old == null ? new NamedUnit(name, scale, base) : old;
88   }
89
90   public static NamedUnit make (String JavaDoc name, Quantity value)
91   {
92     double scale;
93     if (value instanceof DQuantity)
94       scale = ((DQuantity) value).factor;
95     else if (value.imValue() != 0.0)
96       throw new ArithmeticException JavaDoc("defining " + name
97                     + " using complex value");
98     else
99       scale = value.re().doubleValue();
100     Unit base = value.unit();
101     NamedUnit old = lookup(name, scale, base);
102     return old == null ? new NamedUnit(name, scale, base) : old;
103   }
104
105   /**
106    * @serialData Write the unit name (using writeUTF), followed by
107    * the definition (value) of this unit as a scale followed by a base.
108    */
109
110   public void writeExternal(ObjectOutput out) throws IOException
111   {
112     out.writeUTF(name);
113     out.writeDouble(scale);
114     out.writeObject(base);
115   }
116
117   public void readExternal(ObjectInput in)
118     throws IOException, ClassNotFoundException JavaDoc
119   {
120     name = in.readUTF();
121     scale = in.readDouble();
122     base = (Unit) in.readObject();
123   }
124
125   public Object JavaDoc readResolve() throws ObjectStreamException
126   {
127     NamedUnit unit = lookup(name, scale, base);
128     if (unit != null)
129       return unit;
130     init();
131     return this;
132   }
133 }
134
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