/* * Copyright (c) 1998, 2024, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ /** * Provides classes that are fundamental to the design of the Java * programming language. The most important classes are {@link * Object}, which is the root of the class hierarchy, and {@link * Class}, instances of which represent classes at run time. * *
Frequently it is necessary to represent a * value of primitive type as if it were an object.The {@index * "wrapper classes"} {@link Boolean}, {@link Byte}, {@link * Character}, {@link Short}, {@link Integer}, {@link Long}, {@link * Float}, and {@link Double} serve this purpose. An object of type * {@code Double}, for example, contains a field whose type is {@code * double}, representing that value in such a way that a reference to * it can be stored in a variable of reference type. As discussed in * The Java Language Specification, the wrapper classes * are involved in boxing (JLS {@jls 5.1.7}) and unboxing (JLS {@jls * 5.1.8}) conversions. These classes provide a number of methods for * converting among primitive values, as well as methods supporting * such standard functionality as {@code equals} and {@code hashCode}. * The {@link Void} class is a non-instantiable class that holds a * reference to a {@code Class} object representing the type {@code * void}. * *
The class {@link Math} provides commonly used mathematical * functions such as {@linkplain Math#sin(double) sine}, {@linkplain * Math#cos(double) cosine}, and {@linkplain Math#sqrt(double) square * root}. The classes {@link String}, {@link StringBuffer}, and {@link * StringBuilder} similarly provide commonly used operations on * character strings. * *
Classes {@link ClassLoader}, {@link Process}, {@link ProcessBuilder}, * {@link Runtime}, and {@link System} provide "system operations" that * manage the dynamic loading of classes, creation of external processes, * and host environment inquiries such as the time of day. * *
Class {@link Throwable} encompasses objects that may be thrown * by the {@code throw} statement. Subclasses of {@code Throwable} * represent errors and exceptions. * * *