Java example source code file (FailingConstructors.java)

This example Java source code file (FailingConstructors.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

assertionerror, failingconstructorstest, file, file_contents, fileinputstream, illegalargumentexception, ioexception, nullpointerexception, scanner, some, string, this, throwable, unsupported_charset, util

The FailingConstructors.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 7000511
 * @summary PrintStream, PrintWriter, Formatter, Scanner leave files open when
 *          exception thrown
 */

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.nio.file.Files;
import java.util.Scanner;

public class FailingConstructors {
    static final String fileName = "FailingConstructorsTest";
    static final String UNSUPPORTED_CHARSET = "unknownCharset";
    static final String FILE_CONTENTS = "This is a small file!";

    private static void realMain(String[] args) throws Throwable {
        test(false, new File(fileName));

        /* create the file and write its contents */
        File file = File.createTempFile(fileName, null);
        file.deleteOnExit();
        Files.write(file.toPath(), FILE_CONTENTS.getBytes());

        test(true, file);
        file.delete();
    }

    private static void test(boolean exists, File file) throws Throwable {
        /* Scanner(File source, String charsetName) */
        try {
            new Scanner(file, UNSUPPORTED_CHARSET);
            fail();
        } catch(FileNotFoundException|IllegalArgumentException e) {
            pass();
        }

        check(exists, file);

        try {
            new Scanner(file, null);
            fail();
        } catch(FileNotFoundException|NullPointerException e) {
            pass();
        }

        check(exists, file);

        /* Scanner(FileRef source, String charsetName) */
        try {
            new Scanner(file.toPath(), UNSUPPORTED_CHARSET);
            fail();
        } catch(FileNotFoundException|IllegalArgumentException  e) {
            pass();
        }

        check(exists, file);

        try {
            new Scanner(file.toPath(), null);
            fail();
        } catch(FileNotFoundException|NullPointerException e) {
            pass();
        }

        check(exists, file);
    }

    private static void check(boolean exists, File file) {
        if (exists) {
            /* the file should be unchanged */
            verifyContents(file);
        } else {
            /* the file should not have been created */
            if (file.exists()) { fail(file + " should not have been created"); }
        }
    }

    private static void verifyContents(File file) {
        try (FileInputStream fis = new FileInputStream(file)) {
            byte[] contents = FILE_CONTENTS.getBytes();
            int read, count = 0;
            while ((read = fis.read()) != -1) {
                if (read != contents[count++])  {
                    fail("file contents have been altered");
                    return;
                }
            }
        } catch (IOException ioe) {
            unexpected(ioe);
        }
    }

    //--------------------- Infrastructure ---------------------------
    static volatile int passed = 0, failed = 0;
    static void pass() {passed++;}
    static void fail() {failed++; Thread.dumpStack();}
    static void fail(String message) {System.out.println(message); fail(); }
    static void unexpected(Throwable t) {failed++; t.printStackTrace();}
    public static void main(String[] args) throws Throwable {
        try {realMain(args);} catch (Throwable t) {unexpected(t);}
        System.out.printf("%nPassed = %d, failed = %d%n%n", passed, failed);
        if (failed > 0) throw new AssertionError("Some tests failed");}
}