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PMD is an extensible multilanguage static code analyzer. It finds common programming flaws like unused variables, empty catch blocks, unnecessary object creation, and so forth. It's mainly concerned with Java and Apex, but supports 16 other languages. It comes with 400+ built-in rules. It can be extended with custom rules. It uses JavaCC and Antlr to parse source files into abstract syntax trees (AST) and runs rules against them to find violations. Rules can be written in Java or using a XPath query. Currently, PMD supports Java, JavaScript, Salesforce.com Apex and Visualforce, Kotlin, Swift, Modelica, PLSQL, Apache Velocity, JSP, WSDL, Maven POM, HTML, XML and XSL. Scala is supported, but there are currently no Scala rules available. Additionally, it includes CPD, the copy-paste-detector. CPD finds duplicated code in Coco, C/C++, C#, Dart, Fortran, Gherkin, Go, Groovy, HTML, Java, JavaScript, JSP, Julia, Kotlin, Lua, Matlab, Modelica, Objective-C, Perl, PHP, PLSQL, Python, Ruby, Salesforce.com Apex and Visualforce, Scala, Swift, T-SQL, Typescript, Apache Velocity, WSDL, XML and XSL.

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/*
 * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
 */

package net.sourceforge.pmd.util;

import java.io.Closeable;
import java.util.function.Consumer;

/**
 * Base class for an autocloseable that produce a result once it has
 * been closed. None of the methods of this class are synchronized.
 *
 * @param  Type of the result
 */
public abstract class BaseResultProducingCloseable implements AutoCloseable {

    private boolean closed;

    protected final void ensureOpen() {
        AssertionUtil.validateState(!closed, "Listener has been closed");
    }

    /**
     * Returns the result.
     *
     * @throws IllegalStateException If this instance has not been closed yet
     */
    public final T getResult() {
        AssertionUtil.validateState(closed, "Cannot get result before listener is closed");

        return getResultImpl();
    }

    /** Produce the final result. */
    protected abstract T getResultImpl();

    /**
     * Close this object. Idempotent.
     *
     * @implNote Override {@link #closeImpl()} instead.
     */
    @Override
    public final void close() {
        if (!closed) {
            closed = true;
            closeImpl();
        }
    }

    /**
     * Close this closeable as per the contract of {@link Closeable#close()}.
     * Called exactly once. By default does nothing.
     */
    protected void closeImpl() {
        // override
    }

    public static > U using(C closeable, Consumer it) {
        try {
            it.accept(closeable);
        } finally {
            closeable.close();
        }
        return closeable.getResult();
    }
}