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Work on iluwatar#385, created project and provided two mute methods
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‎mute-idiom/pom.xml

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<?xml version="1.0"?>
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<!--
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The MIT License
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Copyright (c) 2014 Ilkka Seppälä
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in
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all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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THE SOFTWARE.
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-->
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<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
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<modelVersion>4.0.0</modelVersion>
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<parent>
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<groupId>com.iluwatar</groupId>
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<artifactId>java-design-patterns</artifactId>
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<version>1.11.0-SNAPSHOT</version>
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</parent>
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<artifactId>mute-idiom</artifactId>
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<dependencies>
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<dependency>
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<groupId>junit</groupId>
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<artifactId>junit</artifactId>
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<scope>test</scope>
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</dependency>
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<dependency>
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<groupId>org.mockito</groupId>
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<artifactId>mockito-core</artifactId>
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<scope>test</scope>
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</dependency>
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</dependencies>
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</project>

‎mute-idiom/src/main/java/com/iluwatar/mute/App.java

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/**
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* The MIT License
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* Copyright (c) 2014 Ilkka Seppälä
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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package com.iluwatar.mute;
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import java.io.ByteArrayOutputStream;
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import java.sql.Connection;
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import java.sql.SQLException;
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public class App {
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public static void main(String[] args) {
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useOfLoggedMute();
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useOfMute();
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}
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/*
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* Typically used when the API declares some exception but cannot do so. Usually a signature mistake.
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* In this example out is not supposed to throw exception as it is a ByteArrayOutputStream. So we
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* utilize mute, which will throw AssertionError if unexpected exception occurs.
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*/
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private static void useOfMute() {
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ByteArrayOutputStream out = new ByteArrayOutputStream();
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Mute.mute(() -> out.write("Hello".getBytes()));
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}
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private static void useOfLoggedMute() {
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Connection connection = openConnection();
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try {
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readStuff(connection);
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} catch (SQLException ex) {
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ex.printStackTrace();
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} finally {
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closeConnection(connection);
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}
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}
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/*
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* All we can do while failed close of connection is to log it.
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*/
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private static void closeConnection(Connection connection) {
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if (connection != null) {
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Mute.loggedMute(() -> connection.close());
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}
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}
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private static void readStuff(Connection connection) throws SQLException {
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if (connection != null) {
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connection.createStatement();
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}
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}
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private static Connection openConnection() {
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return null;
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}
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}

‎mute-idiom/src/main/java/com/iluwatar/mute/CheckedRunnable.java

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/**
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* The MIT License
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* Copyright (c) 2014 Ilkka Seppälä
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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package com.iluwatar.mute;
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/**
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* A runnable which may throw exception on execution.
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*
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*/
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@FunctionalInterface
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public interface CheckedRunnable {
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/**
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* Same as {@link Runnable#run()} with a possibility of exception in execution.
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* @throws Exception if any exception occurs.
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*/
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public void run() throws Exception;
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}

‎mute-idiom/src/main/java/com/iluwatar/mute/Mute.java

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/**
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* The MIT License
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* Copyright (c) 2014 Ilkka Seppälä
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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package com.iluwatar.mute;
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import java.io.ByteArrayOutputStream;
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import java.io.IOException;
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/**
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* A utility class that allows you to utilize mute idiom.
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*/
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public final class Mute {
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/**
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* Executes the <code>runnable</code> and throws the exception occurred within a {@link AssertionError}.
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* This method should be utilized to mute the operations that are guaranteed not to throw an exception.
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* For instance {@link ByteArrayOutputStream#write(byte[])} declares in it's signature that it can throw
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* an {@link IOException}, but in reality it cannot. This is because the bulk write method is not overridden
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* in {@link ByteArrayOutputStream}.
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*
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* @param runnable a runnable that should never throw an exception on execution.
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*/
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public static void mute(CheckedRunnable runnable) {
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try {
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runnable.run();
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} catch (Exception e) {
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throw new AssertionError(e);
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}
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}
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/**
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* Executes the <code>runnable</code> and logs the exception occurred on {@link System#err}.
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* This method should be utilized to mute the operations about which most you can do is log.
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* For instance while closing a connection to database, all you can do is log the exception
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* occurred.
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*
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* @param runnable a runnable that may throw an exception on execution.
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*/
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public static void loggedMute(CheckedRunnable runnable) {
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try {
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runnable.run();
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} catch (Exception e) {
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e.printStackTrace();
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}
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}
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}

‎mute-idiom/src/test/java/com/iluwatar/mute/AppTest.java

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package com.iluwatar.mute;
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import org.junit.Test;
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/**
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* Tests that Mute idiom example runs without errors.
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*
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*/
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public class AppTest {
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@Test
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public void test() {
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App.main(null);
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}
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}

‎mute-idiom/src/test/java/com/iluwatar/mute/MuteTest.java

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/**
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* The MIT License
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* Copyright (c) 2014 Ilkka Seppälä
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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package com.iluwatar.mute;
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import static org.junit.Assert.assertTrue;
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import java.io.ByteArrayOutputStream;
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import java.io.IOException;
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import java.io.PrintStream;
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import org.junit.Rule;
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import org.junit.Test;
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import org.junit.rules.ExpectedException;
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public class MuteTest {
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private static final String MESSAGE = "should not occur";
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@Rule public ExpectedException exception = ExpectedException.none();
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@Test
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public void muteShouldRethrowUnexpectedExceptionAsAssertionError() throws Exception {
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exception.expect(AssertionError.class);
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exception.expectMessage(MESSAGE);
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Mute.mute(() -> methodThrowingException());
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}
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private void methodThrowingException() throws Exception {
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throw new Exception(MESSAGE);
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}
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@Test
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public void loggedMuteShouldLogExceptionTraceBeforeSwallowingIt() throws IOException {
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ByteArrayOutputStream stream = new ByteArrayOutputStream();
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System.setErr(new PrintStream(stream));
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Mute.loggedMute(() -> methodThrowingException());
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assertTrue(new String(stream.toByteArray()).contains(MESSAGE));
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}
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}

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