1 /*
2 * Copyright 1999-2007 Sun Microsystems, Inc. All Rights Reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Sun designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Sun in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 * CA 95054 USA or visit www.sun.com if you need additional information or
23 * have any questions.
24 */
25
26 package java.math;
27
28 /**
29 * A class used to represent multiprecision integers that makes efficient
30 * use of allocated space by allowing a number to occupy only part of
31 * an array so that the arrays do not have to be reallocated as often.
32 * When performing an operation with many iterations the array used to
33 * hold a number is only increased when necessary and does not have to
34 * be the same size as the number it represents. A mutable number allows
35 * calculations to occur on the same number without having to create
36 * a new number for every step of the calculation as occurs with
37 * BigIntegers.
38 *
39 * Note that SignedMutableBigIntegers only support signed addition and
40 * subtraction. All other operations occur as with MutableBigIntegers.
41 *
42 * @see BigInteger
43 * @author Michael McCloskey
44 * @since 1.3
45 */
46
47 class SignedMutableBigInteger extends MutableBigInteger {
48
49 /**
50 * The sign of this MutableBigInteger.
51 */
52 int sign = 1;
53
54 // Constructors
55
56 /**
57 * The default constructor. An empty MutableBigInteger is created with
58 * a one word capacity.
59 */
60 SignedMutableBigInteger() {
61 super();
62 }
63
64 /**
65 * Construct a new MutableBigInteger with a magnitude specified by
66 * the int val.
67 */
68 SignedMutableBigInteger(int val) {
69 super(val);
70 }
71
72 /**
73 * Construct a new MutableBigInteger with a magnitude equal to the
74 * specified MutableBigInteger.
75 */
76 SignedMutableBigInteger(MutableBigInteger val) {
77 super(val);
78 }
79
80 // Arithmetic Operations
81
82 /**
83 * Signed addition built upon unsigned add and subtract.
84 */
85 void signedAdd(SignedMutableBigInteger addend) {
86 if (sign == addend.sign)
87 add(addend);
88 else
89 sign = sign * subtract(addend);
90
91 }
92
93 /**
94 * Signed addition built upon unsigned add and subtract.
95 */
96 void signedAdd(MutableBigInteger addend) {
97 if (sign == 1)
98 add(addend);
99 else
100 sign = sign * subtract(addend);
101
102 }
103
104 /**
105 * Signed subtraction built upon unsigned add and subtract.
106 */
107 void signedSubtract(SignedMutableBigInteger addend) {
108 if (sign == addend.sign)
109 sign = sign * subtract(addend);
110 else
111 add(addend);
112
113 }
114
115 /**
116 * Signed subtraction built upon unsigned add and subtract.
117 */
118 void signedSubtract(MutableBigInteger addend) {
119 if (sign == 1)
120 sign = sign * subtract(addend);
121 else
122 add(addend);
123 if (intLen == 0)
124 sign = 1;
125 }
126
127 /**
128 * Print out the first intLen ints of this MutableBigInteger's value
129 * array starting at offset.
130 */
131 public String toString() {
132 BigInteger b = new BigInteger(this, sign);
133 return
134 b.toString();
135 }
136
137 }
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