137 lines
3.2 KiB
Plaintext
137 lines
3.2 KiB
Plaintext
This rule raises an issue when `Thread.run()` is called instead of `Thread.start()`.
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== Why is this an issue?
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The likely intention of a user calling `Thread.run()` is to start the execution of code within a new thread.
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This, however, is not what happens when this method is called.
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The purpose of `Thread.run()` is to provide a method that users can overwrite to specify the code to be executed.
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The actual thread is then started by calling `Thread.start()`.
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When `Thread.run()` is called directly, it will be executed as a regular method within the current thread.
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== How to fix it
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If you intend to execute the contents of the `Thread.run()` method within a new thread,
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call `Thread.start()` instead.
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If your intention is only to have a container for a method but execute this method within the current thread,
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do not use `Thread` but `Runnable` or another functional interface.
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=== Code examples
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==== Noncompliant code example
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[source,java,diff-id=1,diff-type=noncompliant]
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----
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Thread myThread = new Thread(runnable);
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myThread.run(); // Noncompliant, does not start a thread
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----
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==== Compliant solution
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[source,java,diff-id=1,diff-type=compliant]
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----
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Thread myThread = new Thread(runnable);
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myThread.start(); // Compliant
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----
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==== Noncompliant code example
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[source,java,diff-id=2,diff-type=noncompliant]
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----
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class ComputePrimesThread extends Thread {
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@Override
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public void run() {
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// ...
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}
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}
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new ComputePrimesThread().run(); // Noncompliant, does not start a thread
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----
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==== Compliant solution
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[source,java,diff-id=2,diff-type=compliant]
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----
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class ComputePrimesThread extends Thread {
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@Override
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public void run() {
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// ...
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}
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}
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new ComputePrimesThread().start(); // Compliant
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----
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==== Noncompliant code example
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[source,java,diff-id=3,diff-type=noncompliant]
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----
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class Button {
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private Thread onClick;
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Button(Thread onClick) {
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this.onClick = onClick;
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}
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private void clicked() {
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if (onClick != null) onClick.run(); // Noncompliant, use functional interface
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}
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}
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new Button(new Thread() {
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@Override public void run() {
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System.out.println("clicked!");
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}
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});
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----
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==== Compliant solution
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[source,java,diff-id=3,diff-type=compliant]
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----
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class Button {
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private Runnable onClick;
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Button(Runnable onClick) {
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this.onClick = onClick;
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}
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private void clicked() {
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if (onClick != null) onClick.run(); // compliant
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}
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}
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new Button(() -> System.out.println("clicked!"));
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----
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== Resources
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=== Documentation
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* https://docs.oracle.com/javase/8/docs/api/java/lang/Thread.html#start--[Java™ Platform, Standard Edition 8 API Specification - Thread.start()]
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=== Articles & blog posts
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* https://www.javatpoint.com/what-if-we-call-java-run-method-directly[JavaTPoint - What if we call Java run() method directly instead start() method?]
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ifdef::env-github,rspecator-view[]
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'''
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== Implementation Specification
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(visible only on this page)
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=== Message
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Call the method Thread.start() to execute the content of the run() method in a dedicated thread.
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'''
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== Comments And Links
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(visible only on this page)
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=== on 20 Aug 2013, 15:40:32 Freddy Mallet wrote:
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Is implemented by \http://jira.codehaus.org/browse/SONARJAVA-308
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endif::env-github,rspecator-view[]
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