1 /*
2 * Copyright (c) 1994, 2026, Oracle and/or its affiliates. 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. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.lang;
27
28 /**
29 * The abstract class {@code Number} is the superclass of platform
30 * classes representing numeric values that are convertible to the
31 * primitive types {@code byte}, {@code double}, {@code float}, {@code
32 * int}, {@code long}, and {@code short}.
33 *
34 * The specific semantics of the conversion from the numeric value of
35 * a particular {@code Number} implementation to a given primitive
36 * type is defined by the {@code Number} implementation in question.
37 *
38 * For platform classes, the conversion is often analogous to a
39 * narrowing primitive conversion or a widening primitive conversion
40 * as defined in <cite>The Java Language Specification</cite>
41 * for converting between primitive types. Therefore, conversions may
42 * lose information about the overall magnitude of a numeric value, may
43 * lose precision, and may even return a result of a different sign
44 * than the input.
45 *
46 * See the documentation of a given {@code Number} implementation for
47 * conversion details.
48 *
49 * <div class="preview-block">
50 * <div class="preview-comment">
51 * When preview features are enabled, {@code Number} is
52 * an abstract {@linkplain Class#isValue value class}.
53 * Subclasses of {@code Number} can be either an {@linkplain Class#isIdentity identity class}
54 * or a {@linkplain Class#isValue value class}.
55 * See The Java Language Specification {@jls value-objects-8.1.1.5 Value Classes}.
56 * </div>
57 * </div>
58 *
59 * @author Lee Boynton
60 * @author Arthur van Hoff
61 * @jls 5.1.2 Widening Primitive Conversion
62 * @jls 5.1.3 Narrowing Primitive Conversion
63 * @since 1.0
64 */
65 @jdk.internal.MigratedValueClass
66 public abstract class Number implements java.io.Serializable {
67 /**
68 * Constructor for subclasses to call.
69 */
70 public Number() {super();}
71
72 /**
73 * Returns the value of the specified number as an {@code int}.
74 *
75 * @return the numeric value represented by this object after conversion
76 * to type {@code int}.
77 */
78 public abstract int intValue();
79
80 /**
81 * Returns the value of the specified number as a {@code long}.
82 *
83 * @return the numeric value represented by this object after conversion
84 * to type {@code long}.
85 */
86 public abstract long longValue();
87
88 /**
89 * Returns the value of the specified number as a {@code float}.
90 *
91 * @return the numeric value represented by this object after conversion
92 * to type {@code float}.
93 */
94 public abstract float floatValue();
95
96 /**
97 * Returns the value of the specified number as a {@code double}.
98 *
99 * @return the numeric value represented by this object after conversion
100 * to type {@code double}.
101 */
102 public abstract double doubleValue();
103
104 /**
105 * Returns the value of the specified number as a {@code byte}.
106 *
107 * @implSpec
108 * The default implementation returns the result of {@link #intValue} cast
109 * to a {@code byte}.
110 *
111 * @return the numeric value represented by this object after conversion
112 * to type {@code byte}.
113 * @since 1.1
114 */
115 public byte byteValue() {
116 return (byte)intValue();
117 }
118
119 /**
120 * Returns the value of the specified number as a {@code short}.
121 *
122 * @implSpec
123 * The default implementation returns the result of {@link #intValue} cast
124 * to a {@code short}.
125 *
126 * @return the numeric value represented by this object after conversion
127 * to type {@code short}.
128 * @since 1.1
129 */
130 public short shortValue() {
131 return (short)intValue();
132 }
133
134 /** use serialVersionUID from JDK 1.0.2 for interoperability */
135 @java.io.Serial
136 private static final long serialVersionUID = -8742448824652078965L;
137 }