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POunsafe operation, unchecked conversion
 

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  1. POunsafe operation, unchecked conversion
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    <p>When I compile the following class (available <a href="https://github.com/lviggiano/owner/blob/master/src/test/java/org/aeonbits/owner/multithread/ThreadBase.java" rel="nofollow">here</a>, the main method has been added to reproduce the problem in a single class), I get the following compiler warning in IntelliJ or from maven command line:</p> <pre><code>java: /Users/luigi/var/src/owner/src/test/java/org/aeonbits/owner/multithread/ThreadBase.java uses unchecked or unsafe operations. java: Recompile with -Xlint:unchecked for details. </code></pre> <p>Then I added the -Xlint:unchecked to maven to see the details and I got this:</p> <pre><code>[WARNING] /Users/luigi/var/src/owner/src/test/java/org/aeonbits/owner/multithread/ThreadBase.java:[74,45] unchecked conversion required: java.util.List&lt;java.lang.Throwable&gt; found: java.util.List </code></pre> <p>The class source follows (the main has been added to reproduce the problem in a single class):</p> <pre><code>package org.aeonbits.owner.multithread; import org.aeonbits.owner.Config; import org.aeonbits.owner.UtilTest.MyCloneable; import java.util.ArrayList; import java.util.List; import static org.aeonbits.owner.UtilTest.debug; abstract class ThreadBase&lt;T extends Config&gt; extends Thread implements MyCloneable { private static long counter = 0; final long uniqueThreadId = ++counter; final T cfg; final Object lock; final int loops; final List&lt;Throwable&gt; errors = new ArrayList&lt;Throwable&gt;(); ThreadBase(T cfg, Object lock, int loops) { this.cfg = cfg; this.lock = lock; this.loops = loops; } @Override public Object clone() throws CloneNotSupportedException { return super.clone(); } @Override public void run() { synchronized (lock) { try { lock.wait(); } catch (InterruptedException e) { Thread.currentThread().interrupt(); return; } } for (int i = 0; i &lt; loops; i++) { debug("%s[%d] started loop #%d.\n", getClass().getName(), uniqueThreadId, i); try { execute(); } catch (Throwable throwable) { debug("%s[%d] thrown an error in loop #%d.\n", getClass().getName(), uniqueThreadId, i); errors.add(throwable); } yield(); debug("%s[%d] completed loop #%d.\n", getClass().getName(), uniqueThreadId, i); } } abstract void execute() throws Throwable; public List&lt;Throwable&gt; getErrors() { return errors; } public static void main(String[] args) { ThreadBase t = new ThreadBase(null, new Object(), 10) { @Override void execute() throws Throwable { } }; List&lt;Throwable&gt; errors = t.getErrors(); // ^ compiler reports the warning here! } } </code></pre> <p>Additional details:</p> <pre><code>$ mvn --version Apache Maven 3.0.4 (r1232337; 2012-01-17 09:44:56+0100) Maven home: /Users/luigi/opt/apache-maven-3.0.4 Java version: 1.7.0_25, vendor: Oracle Corporation Java home: /Library/Java/JavaVirtualMachines/jdk1.7.0_25.jdk/Contents/Home/jre Default locale: en_US, platform encoding: UTF-8 OS name: "mac os x", version: "10.8.4", arch: "x86_64", family: "mac" </code></pre> <p>In pom.xml I added compiler.source and compiler.target 1.5 since my library is targetted to jdk 1.5 or better:</p> <pre><code>&lt;build&gt; &lt;pluginManagement&gt; &lt;plugins&gt; &lt;plugin&gt; &lt;groupId&gt;org.apache.maven.plugins&lt;/groupId&gt; &lt;artifactId&gt;maven-compiler-plugin&lt;/artifactId&gt; &lt;version&gt;3.1&lt;/version&gt; &lt;configuration&gt; &lt;source&gt;1.5&lt;/source&gt; &lt;target&gt;1.5&lt;/target&gt; &lt;compilerArgument&gt;-Xlint:unchecked&lt;/compilerArgument&gt; &lt;/configuration&gt; &lt;/plugin&gt; &lt;/plugins&gt; &lt;/pluginManagement&gt; </code></pre> <p>Can anybody explain me what is wrong here?</p> <p>For me, it does not make any sense as t.getErrors() returns a List:</p> <pre><code>List&lt;Throwable&gt; errors = t.getErrors(); </code></pre> <p>What's wrong here?!?</p>
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    1. USLuigi R. Viggiano
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    1. COyou don't need to generify ThreadBase, `T` is useless. simply `final Config cfg; ... ThreadBase(Config cfg...)`
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      1. POunsafe operation, unchecked conversion
      1. USZhongYu
    2. COThe field `T cfg` is declared with default accessibility, in subclasses I use the type `T`, so this is why `T` is not useless. Btw, this is irrelevant to the question I asked, and it does not provide any answer.
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      1. POunsafe operation, unchecked conversion
      1. USLuigi R. Viggiano
 

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