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Java example source code file (TestTypeParameter.java)

This example Java source code file (TestTypeParameter.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

class, element, elementscanner7, integer, intf, javactestingabstractprocessor, list, override, testtypeparameter, typeelement, typeparameterelement, util, void

The TestTypeParameter.java Java example source code

/*
 * Copyright (c) 2011, 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.
 *
 * 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.
 */

/*
 * @test
 * @bug 6505047
 * @summary javax.lang.model.element.Element.getEnclosingElement() doesn't return null for type parameter
 * @library /tools/javac/lib
 * @build JavacTestingAbstractProcessor TestTypeParameter
 * @compile -processor TestTypeParameter -proc:only TestTypeParameter.java
 */

import java.util.*;
import javax.annotation.processing.*;
import javax.lang.model.element.*;
import javax.lang.model.util.*;
import javax.tools.*;

public class TestTypeParameter<T> extends JavacTestingAbstractProcessor {
    int round = 0;

    public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
        if (++round == 1) {
            int found = (new Scanner()).scan(roundEnv.getRootElements(), null);
            if (found == expect) {
                note("generic elements found and verified: " + found);
            } else {
                error("unexpected number of results: expected " + expect
                        + ", found " + found);
            }

        }
        return true;
    }

    class Scanner extends ElementScanner7<Integer,Void> {
        @Override
        public Integer visitExecutable(ExecutableElement e, Void p) {
            super.visitExecutable(e, p);
            found += check(e, e.getTypeParameters());
            return found;
        }

        @Override
        public Integer visitType(TypeElement e, Void p) {
            super.visitType(e, p);
            found += check(e, e.getTypeParameters());
            return found;
        }

        int found;
    }

    /**
     * Check if type parameters, if any, have expected owner.
     * Return 1 if typarams not empty and all have expected owner, else return 0.
     */
    int check(Element e, List<? extends TypeParameterElement> typarams) {
        note("checking " + e, e);
        if (typarams.isEmpty()) {
            note("no type parameters found", e);
            return 0;
        }
        for (TypeParameterElement tpe: typarams) {
            note("checking type parameter " + tpe, tpe);
            if (tpe.getEnclosingElement() != e) {
                error("unexpected owner; expected: " + e
                        + ", found " + tpe.getEnclosingElement(),
                        tpe);
                return 0;
            }
            if (tpe.getEnclosingElement() != tpe.getGenericElement()) {
                error("unexpected generic element; expected: " + tpe.getGenericElement()
                        + ", found " + tpe.getEnclosingElement(),
                        tpe);
                return 0;
            }
        }
        note("verified " + e, e);
        return 1;
    }

    void note(String msg) {
        messager.printMessage(Diagnostic.Kind.NOTE, msg);
    }

    void note(String msg, Element e) {
        messager.printMessage(Diagnostic.Kind.NOTE, msg, e);
    }

    void error(String msg, Element e) {
        messager.printMessage(Diagnostic.Kind.ERROR, msg, e);
    }

    void error(String msg) {
        messager.printMessage(Diagnostic.Kind.ERROR, msg);
    }

    // additional generic elements to test
    <X> X m(X x) { return x; }

    interface Intf<X> { X m() ; }

    class Class<X> {
        <Y> Class() { }
    }

    final int expect = 5;  // top level class, plus preceding examples
}

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