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/*
* Copyright (c) 2015, 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 interfaces for creating tools, such as a Read-Eval-Print Loop (REPL),
* which interactively evaluate "snippets" of Java programming language code.
* Where a "snippet" is a single expression, statement, or declaration.
* This functionality can be used to enhance tools such as IDEs or can be
* stand-alone.
*
* {@link jdk.jshell.JShell} is the central class. An instance of
* JShell holds the evaluation state, which is both the current
* set of source snippets and the execution state they have produced.
*
* Each source snippet is represented by an instance of a subclass of
* {@link jdk.jshell.Snippet}. For example, a statement is represented by an
* instance of {@link jdk.jshell.StatementSnippet}, and a method declaration is
* represented by an instance of {@link jdk.jshell.MethodSnippet}.
* Snippets are created when {@link jdk.jshell.JShell#eval(java.lang.String)}
* is invoked with an input which includes one or more snippets of code.
*
* Any change to the compilation status of a snippet is reported with a
* {@link jdk.jshell.SnippetEvent}. There are three major kinds of
* changes to the status of a snippet: it can created with eval,
* it can be dropped from the active source state with
* {@link jdk.jshell.JShell#drop(jdk.jshell.PersistentSnippet)}, and it can have
* its status updated as a result of a status change in another snippet.
* For
* example: given js, an instance of JShell, executing
* js.eval("int x = 5;") will add the variable x to
* the source state and will generate an event describing the creation of a
* {@link jdk.jshell.VarSnippet} for x. Then executing
* js.eval("int timesx(int val) { return val * x; }") will add
* a method to the source state and will generate an event
* describing the creation of a {@link jdk.jshell.MethodSnippet} for
* timesx.
* Assume that varx holds the snippet created by the first
* call to eval, executing js.drop(varx) will
* generate two events: one for changing the status of the
* variable snippet to DROPPED and one for
* updating the method snippet (which now has an unresolved reference to
* x).
*
* Of course, for any general application of the API, the input would not be
* fixed strings, but would come from the user. Below is a very simplified
* example of how the API might be used to implement a REPL.
*
* {@code
* import java.io.ByteArrayInputStream;
* import java.io.Console;
* import java.util.List;
* import jdk.jshell.*;
* import jdk.jshell.Snippet.Status;
*
* class ExampleJShell {
* public static void main(String[] args) {
* Console console = System.console();
* try (JShell js = JShell.create()) {
* do {
* System.out.print("Enter some Java code: ");
* String input = console.readLine();
* if (input == null) {
* break;
* }
* List<SnippetEvent> events = js.eval(input);
* for (SnippetEvent e : events) {
* StringBuilder sb = new StringBuilder();
* if (e.causeSnippet == null) {
* // We have a snippet creation event
* switch (e.status) {
* case VALID:
* sb.append("Successful ");
* break;
* case RECOVERABLE_DEFINED:
* sb.append("With unresolved references ");
* break;
* case RECOVERABLE_NOT_DEFINED:
* sb.append("Possibly reparable, failed ");
* break;
* case REJECTED:
* sb.append("Failed ");
* break;
* }
* if (e.previousStatus == Status.NONEXISTENT) {
* sb.append("addition");
* } else {
* sb.append("modification");
* }
* sb.append(" of ");
* sb.append(e.snippet.source());
* System.out.println(sb);
* if (e.value != null) {
* System.out.printf("Value is: %s\n", e.value);
* }
* System.out.flush();
* }
* }
* } while (true);
* }
* System.out.println("\nGoodbye");
* }
* }
* }
*
*
* To register for status change events use
* {@link jdk.jshell.JShell#onSnippetEvent(java.util.function.Consumer)}.
* These events are only generated by eval and drop,
* the return values of these methods are the list of events generated by that
* call. So, as in the example above, events can be used without registering
* to receive events.
*
* If you experiment with this example, you will see that failing to terminate
* a statement or variable declaration with a semi-colon will simply fail.
* An unfinished entry (for example a desired multi-line method) will also just
* fail after one line. The utilities in {@link jdk.jshell.SourceCodeAnalysis}
* provide source boundary and completeness analysis to address cases like
* those. SourceCodeAnalysis also provides suggested completions
* of input, as might be used in tab-completion.
*/
package jdk.jshell;