Most likely due to [JDK-6609854][1] and [JDK-8189343][2] which reported negative nested character classes handling (in your example `[^[0-9-]]`). This behavior was fixed in 9 and 10, but fix was not backported to 8. The bug for Java 8 is explained as:

&gt; In Java, the negation does _not_ apply to anything appearing in
&gt; nested `[brackets]`
&gt; 
&gt; So `[^c]` does not match &quot;c&quot;, as you would expect.
&gt;
&gt; **`[^[c]]` does match &quot;c&quot;. Not what I would expect.**
&gt;
&gt; `[[^c]]` does not match &quot;c&quot;
&gt; 
&gt; The same holds true for ranges or property expressions - if they&#39;re
&gt; inside brackets, a negation at an out level does not affect them.
&gt;
&gt; `[^a-z]` is opposite from `[^[a-z]]`


  [1]: https://bugs.openjdk.java.net/browse/JDK-6609854
  [2]: https://bugs.openjdk.java.net/browse/JDK-8189343

There is a previous question (https://stackoverflow.com/questions/48167955/docker-unknown-flag-mount) facing the same error that was due to having an out-of-date version of Docker running. I have an up-to-date version of Docker running.

I have the following `Dockerfile`:

    FROM continuumio/miniconda3
    
    RUN --mount=type=ssh pip install git+ssh://git@github.com/myrepo/myproject.git@develop
    RUN conda install numpy
    ...

According to the [documentation][1], I should be able to simply run `docker build --ssh default .`. However, I receive the following error:

    Sending build context to Docker daemon  2.048kB
    Error response from daemon: Dockerfile parse error line 3: Unknown flag: mount

Output of `docker version`:

    Client: Docker Engine - Community
     Version:           18.09.2
     API version:       1.39
     Go version:        go1.10.8
     Git commit:        6247962
     Built:             Sun Feb 10 04:12:39 2019
     OS/Arch:           darwin/amd64
     Experimental:      false
    
    Server: Docker Engine - Community
     Engine:
      Version:          18.09.2
      API version:      1.39 (minimum version 1.12)
      Go version:       go1.10.6
      Git commit:       6247962
      Built:            Sun Feb 10 04:13:06 2019
      OS/Arch:          linux/amd64
      Experimental:     true

I would like to build a Docker image without exposing my private SSH credentials, and this seemed to be the supported method. Anyone have thoughts on what&#39;s causing the issue?

  [1]: https://docs.docker.com/develop/develop-images/build_enhancements/#using-ssh-to-access-private-data-in-builds

Error response from daemon: Dockerfile parse error Unknown flag: mount

I run into two challenges:


- Even if, as per React guideline, **derived state** is discouraged, but some edge cases still need it.   
In terms of a functional component with React Hook, **What is the equivalent implementation with React Hook, If I do need derived state which in class component, will be updated in componentWillReceiveProps on every parent render**

see below code sample:

&lt;!-- begin snippet: js hide: false console: true babel: false --&gt;

&lt;!-- language: lang-js --&gt;

    class App extends Component {
      constructor(props) {
        super(props);
        this.state = {
          count: props.count &gt; 100 ? 100 : props.count,
        }

      }

      /*What is the equivalent implementation when React Hook is used here componentWillReceiveProps*/
      componentWillReceiveProps(nextProps) {
        if (nextProps.count !== this.props.count) {
          this.setState({
            count: nextProps.count &gt; 100 ? 100 : nextProps.count
          });
        }
      }

      render() {
        return ( &lt;
          div &gt; {
            this.state.count
          } &lt;
          /div&gt;
        );
      }
    }

    export default App;

&lt;!-- end snippet --&gt;

- As for componentDidUpdate, componentDidUpdate has its counterpart when React Hook is used, you have to use it like, 

        React.useEffect(() =&gt; {
          return () =&gt; {
            
           };
        }, [parentProp]);

   
   the Second param for useEffect makes sure code is executed only when prop changes, but **what if I want to do respective tasks based on multiple respective props changes**? how to get it done **with useEffect**?

see below code sample:

&lt;!-- begin snippet: js hide: false console: true babel: false --&gt;

&lt;!-- language: lang-js --&gt;

    class App extends Component {


      /*What is the equivalent implementation when functional component with React Hook is used here */
      componentDidUpdate(prevProps, prevState) {
        if (prevProps.groupName !== this.props.groupName) {
          console.log(&#39;Let&#39;
            &#39;s say, I do want to do some task here only when groupName differs&#39;);
        } else if (prevProps.companyName !== this.props.companyName) {
          console.log(&#39;Let&#39;
            &#39;s say, I do want to do some different task here only when companyName differs&#39;);
        }

      }


      render() {
        /*for simplicity, render code is ignored*/
        return null;
      }
    }

    export default App;

&lt;!-- end snippet --&gt;





componentWillReceiveProps, componentDidUpdate for React Hook

Why does this code output `02` in [tag:java-8] but `o2` in [tag:java-9] or above?

    &quot;o2&quot;.replaceAll(&quot;([oO])([^[0-9-]])&quot;, &quot;0$2&quot;)

Why does String.replaceAll() work differently in Java 8 from Java 9?

Why does this code output <code>02</code> in [tag:java-8] but <code>o2</code> in [tag:java-9] or above?
<pre><code class="hljs language-bash">"o2".replaceAll("([oO])([^[0-9-]])", "0$2")
</code></pre>

I am looking to pick up a docker image to build a java app and looking at the variants of the OpenJDK images available.
I am looking here https://github.com/docker-library/openjdk/tree/master/8/jdk and see alpine, slim and windows.
What are the differences between these and what does each variant give?

Docker images - types. Slim vs slim-stretch vs stretch vs alpine

My JUnit tests are failing when running them through Maven and the Surefire plugin (version information below). I see the error message:

    Corrupted STDOUT by directly writing to native stream in forked JVM 4. See FAQ web page and the dump file C:\(...)\target\surefire-reports\2019-03-20T18-57-17_082-jvmRun4.dumpstream

The FAQ page points out some possible reasons but I don&#39;t see how I can use this information to start solving this problem:

&gt; Corrupted STDOUT by directly writing to native stream in forked JVM
&gt;
&gt; If your tests use native library which prints to STDOUT this warning message appears because the library corrupted the channel used by the plugin in order to transmit events with test status back to Maven process. It would be even worse if you override the Java stream by System.setOut because the stream is also supposed to be corrupted but the Maven will never see the tests finished and build may hang.
&gt;
&gt; This warning message appears if you use FileDescriptor.out or JVM prints GC summary.
&gt;
&gt; In that case the warning is printed &quot;Corrupted STDOUT by directly writing to native stream in forked JVM&quot;, and a dump file can be found in Reports directory.
&gt;
&gt; If debug level is enabled then messages of corrupted stream appear in the console. 


It refers to some native library printing out to STDOUT directly but how can I figure out which one, and even if I do, how do I deal with this issue if I need the library for my project?

It mentions &quot;debug level&quot; but it is unclear if this means Maven&#39;s debug level or Surefire plugin&#39;s debug level. I enabled Maven&#39;s debug but I don&#39;t see the console outputs as mentioned by the FAQ. And Surefire&#39;s debug option seems to be about pausing tests and waiting for a debugger to be connected to the process, not simply showing more information on the console.

The dump files also don&#39;t seem very helpful:

    # Created on 2019-03-20T18:42:58.323
    Corrupted STDOUT by directly writing to native stream in forked JVM 2. Stream &#39;FATAL ERROR in native method: processing of -javaagent failed&#39;.
    java.lang.IllegalArgumentException: Stream stdin corrupted. Expected comma after third character in command &#39;FATAL ERROR in native method: processing of -javaagent failed&#39;.
        at org.apache.maven.plugin.surefire.booterclient.output.ForkClient$OperationalData.&lt;init&gt;(ForkClient.java:511)
        at org.apache.maven.plugin.surefire.booterclient.output.ForkClient.processLine(ForkClient.java:209)
        at org.apache.maven.plugin.surefire.booterclient.output.ForkClient.consumeLine(ForkClient.java:176)
        at org.apache.maven.plugin.surefire.booterclient.output.ThreadedStreamConsumer$Pumper.run(ThreadedStreamConsumer.java:88)
        at java.base/java.lang.Thread.run(Thread.java:834)

So, how can I solve this problem?

**Update**: requested configuration information below.

I&#39;m using OpenJDK 11 (Zulu distribution) on Windows 10, Maven 3.5.3, and Surefire 2.21.0 (full configuration below).

I&#39;m running Maven from Eclipse using the &quot;Run As...&quot; context menu option on the `pom.xml` file, but obtain the same results when running it on the console.

I had never heard of JaCoco before the first comment to this question, but I see several error messages mentioning it:

    [ERROR] ExecutionException The forked VM terminated without properly saying goodbye. VM crash or System.exit called?
    [ERROR] Command was cmd.exe /X /C &quot;&quot;C:\Program Files\Zulu\zulu-11\bin\java&quot; -javaagent:C:\\Users\\E26638\\.m2\\repository\\org\\jacoco\\org.jacoco.agent\\0.8.0\\org.jacoco.agent-0.8.0-runtime.jar=destfile=C:\\Users\\E26638\\git\\aic-expresso\\target\\jacoco.exec -Xms256m -Xmx1028m -jar C:\Users\E26638\AppData\Local\Temp\surefire10089630030045878403\surefirebooter8801585361488929382.jar C:\Users\E26638\AppData\Local\Temp\surefire10089630030045878403 2019-03-21T21-26-04_829-jvmRun12 surefire10858509118810158083tmp surefire_115439010304069944813tmp&quot;
    [ERROR] Error occurred in starting fork, check output in log
    [ERROR] Process Exit Code: 1

This is the Surefire Maven plugin configuration:

        &lt;plugin&gt;
            &lt;groupId&gt;org.apache.maven.plugins&lt;/groupId&gt;
            &lt;artifactId&gt;maven-surefire-plugin&lt;/artifactId&gt;
            &lt;version&gt;2.21.0&lt;/version&gt;
            &lt;configuration&gt;
                &lt;skipTests&gt;${skipUnitTests}&lt;/skipTests&gt;
                &lt;testFailureIgnore&gt;false&lt;/testFailureIgnore&gt;
                &lt;forkCount&gt;1.5C&lt;/forkCount&gt;
                &lt;reuseForks&gt;true&lt;/reuseForks&gt;
                &lt;parallel&gt;methods&lt;/parallel&gt;
                &lt;threadCount&gt;4&lt;/threadCount&gt;
                &lt;perCoreThreadCount&gt;true&lt;/perCoreThreadCount&gt;
                &lt;reportFormat&gt;plain&lt;/reportFormat&gt;
                &lt;trimStackTrace&gt;false&lt;/trimStackTrace&gt;
                &lt;redirectTestOutputToFile&gt;true&lt;/redirectTestOutputToFile&gt;
            &lt;/configuration&gt;
        &lt;/plugin&gt;








Surefire Maven plugin: &quot;Corrupted STDOUT by directly writing to native stream in forked JVM&quot;

I&#39;ve recently come across this unusual (to me) Java syntax...here&#39;s an example of it:

    List list = new &lt;String, Long&gt;ArrayList();

Notice the positioning of the `&lt;String, Long&gt;` type arguments...it&#39;s not after the type as normal but before. I don&#39;t mind admitting I&#39;ve never seen this syntax before. Also note there are 2 type arguments when `ArrayList` only has 1.

Does the positioning of the type arguments have the same meaning as putting them after the type? If not, what does the different positioning mean?

Why is it legal to have 2 type arguments when `ArrayList` only has 1?

I&#39;ve searched the usual places, eg. Angelika Langer and on here but can&#39;t find any mention of this syntax anywhere apart from the grammar rules in the Java grammar file on the ANTLR project.

What do constructor type arguments mean when placed *before* the type?

I want to use `com.google.android.material.tabs.TabLayout` component with Android&#39;s new `ViewPager` implementation `androidx.viewpager2.widget.ViewPager2`. However, the `setupWithViewPager(..)` method provided by `TabLayout` supports only the old `ViewPager` implementation. Is there a way to bind a `TabLayout` to a `ViewPager2` component easily?

How to use TabLayout with ViewPager2 in Android

As part of my investigation on the difference between using a complex filter or multiple filters in streams, I notice that performance on Java 12 is way slower than on Java 8.

Is any explanation for those weird results? Did I miss something here? 

**Configuration:** 

* java 8
  * OpenJDK Runtime Environment (build 1.8.0_181-8u181-b13-2~deb9u1-b13)
  * OpenJDK 64-Bit Server VM (build 25.181-b13, mixed mode)

* java 12
  * OpenJDK Runtime Environment (build 12+33)
  * OpenJDK 64-Bit Server VM (build 12+33, mixed mode, sharing)

* VM options: `-XX:+UseG1GC` `-server` `-Xmx1024m` `-Xms1024m`
* CPU: 8 cores

**JMH Throughput Results**:

* Warmup: 10 iterations, 1 s each
* Measurement: 10 iterations, 1 s each
* Threads: 1 thread, will synchronize iterations
* Units: ops/s

[![Comparison tables][2]][2]

## Code

**Stream + complex filter**

```java
public void complexFilter(ExecutionPlan plan, Blackhole blackhole) {
        long count = plan.getDoubles()
                .stream()
                .filter(d -&gt; d &lt; Math.PI
                        &amp;&amp; d &gt; Math.E
                        &amp;&amp; d != 3
                        &amp;&amp; d != 2)
                .count();

        blackhole.consume(count);
    }
```

**Stream + multiple filters** 

```java
public void multipleFilters(ExecutionPlan plan, Blackhole blackhole) {
        long count = plan.getDoubles()
                .stream()
                .filter(d -&gt; d &gt; Math.PI)
                .filter(d -&gt; d &lt; Math.E)
                .filter(d -&gt; d != 3)
                .filter(d -&gt; d != 2)
                .count();

        blackhole.consume(count);
    }
```

**Parallel stream + complex filter** 

```java
public void complexFilterParallel(ExecutionPlan plan, Blackhole blackhole) {
        long count = plan.getDoubles()
                .stream()
                .parallel()
                .filter(d -&gt; d &lt; Math.PI
                        &amp;&amp; d &gt; Math.E
                        &amp;&amp; d != 3
                        &amp;&amp; d != 2)
                .count();

        blackhole.consume(count);
    }
```

**Parallel stream + multiple filters**

```java
public void multipleFiltersParallel(ExecutionPlan plan, Blackhole blackhole) {
        long count = plan.getDoubles()
                .stream()
                .parallel()
                .filter(d -&gt; d &gt; Math.PI)
                .filter(d -&gt; d &lt; Math.E)
                .filter(d -&gt; d != 3)
                .filter(d -&gt; d != 2)
                .count();

        blackhole.consume(count);
    }

```

**Old fashion java iteration** 

```java
public void oldFashionFilters(ExecutionPlan plan, Blackhole blackhole) {
        long count = 0;
        for (int i = 0; i &lt; plan.getDoubles().size(); i++) {
            if (plan.getDoubles().get(i) &gt; Math.PI
                    &amp;&amp; plan.getDoubles().get(i) &gt; Math.E
                    &amp;&amp; plan.getDoubles().get(i) != 3
                    &amp;&amp; plan.getDoubles().get(i) != 2) {
                count = count + 1;
            }
        }

        blackhole.consume(count);
    }

```

You can try by yourself by running docker command: 

For Java 8: 

&gt; docker run -it volkodav/java-filter-benchmark:java8

For Java 12: 

&gt; docker run -it volkodav/java-filter-benchmark:java12


**Source code:**

https://github.com/volkodavs/javafilters-benchmarks


  [2]: https://i.stack.imgur.com/GTYeu.png

Mystifying microbenchmark result for stream API on Java 12 vs. Java 8 with -gc true

I stumbled across a surprising (to me) fact.

&lt;!-- begin snippet: js hide: false console: true babel: false --&gt;

&lt;!-- language: lang-js --&gt;

    console.log(&quot;asdf&quot;.replace(/.*/g, &quot;x&quot;));

&lt;!-- end snippet --&gt;

Why *two* replacements?  It seems any non-empty string without newlines will produce exactly two replacements for this pattern.  Using a replacement function, I can see that the first replacement is for the entire string, and the second is for an empty string.  

Why is &quot;asdf&quot;.replace(/.*/g, &quot;x&quot;) == &quot;xx&quot;?

I&#39;m a beginner to regex and I am trying to make an expression to find if there are two of the same digits next to each other, and the digit behind and in front of the pair is different.

For example,

123456678 should match as there is a double 6,

1234566678 should not match as there is no double with different surrounding numbers.
12334566 should match because there are two 3s.

So far i have this which works only with 1, and as long as the double is not at the start or end of the string, however I can deal with that by adding a letter at the start and end. 

```
^.*([^1]11[^1]).*$
```

I know i can use `[0-9]` instead of the 1s but the problem is having them all be the same digit. 

Thank you!

regex to find a pair of adjacent digits with different digits around them

I recently had a [SonarQube][1] rule (https://rules.sonarsource.com/java/RSPEC-4784) bring to my attention some performance issues which could be used as a denial of service against a Java regular expression implementation.

Indeed, the following Java test shows how slow the wrong regular expression can be:

```
    import org.junit.Test;

    public class RegexTest {

    @Test
    public void fastRegex1() {
        &quot;aaaaaaaaaaaaaaaaaaaaaaaaaaaabs&quot;.matches(&quot;(a+)b&quot;);
    }

    @Test
    public void fastRegex2() {
        &quot;aaaaaaaaaaaaaaaaaaaaaaaaaaaab&quot;.matches(&quot;(a+)+b&quot;);
    }

    @Test
    public void slowRegex() {
        &quot;aaaaaaaaaaaaaaaaaaaaaaaaaaaabs&quot;.matches(&quot;(a+)+b&quot;);
    }
}
```

As you can see, the first two tests are fast, the third one is incredibly slow (in Java 8)

[![Enter image description here][2]][2]

The same data and regex in Perl or Python, however, is not at all slow, which leads me to wonder why it is that this regular expression is so slow to evaluate in Java.

```
$ time perl -e &#39;&quot;aaaaaaaaaaaaaaaaaaaaaaaaaaaabs&quot; =~ /(a+)+b/ &amp;&amp; print &quot;$1\n&quot;&#39;
aaaaaaaaaaaaaaaaaaaaaaaaaaaa

real    0m0.004s
user    0m0.000s
sys     0m0.004s

$ time python3 -c &#39;import re; m=re.search(&quot;(a+)+b&quot;,&quot;aaaaaaaaaaaaaaaaaaaaaaaaaaaabs&quot;); print(m.group(0))&#39;
aaaaaaaaaaaaaaaaaaaaaaaaaaaab

real    0m0.018s
user    0m0.015s
sys     0m0.004s

```

What is it about the extra matching modifier `+` or trailing character `s` in the data which makes this regular expression so slow, and why is it only specific to Java?

  [1]: https://en.wikipedia.org/wiki/SonarQube
  [2]: https://i.stack.imgur.com/5bUNZ.png


Why is this regular expression so slow in Java?

I have to create a function which takes a string, and it should return `true` or `false` based on whether the input consists of a repeated character sequence. The length of the given string is always greater than `1` and the character sequence must have at least one repetition.

    &quot;aa&quot; // true(entirely contains two strings &quot;a&quot;)
    &quot;aaa&quot; //true(entirely contains three string &quot;a&quot;)
    &quot;abcabcabc&quot; //true(entirely containas three strings &quot;abc&quot;)

    &quot;aba&quot; //false(At least there should be two same substrings and nothing more)
    &quot;ababa&quot; //false(&quot;ab&quot; exists twice but &quot;a&quot; is extra so false)

I have created the below function:

&lt;!-- begin snippet: js hide: false console: true babel: false --&gt;

&lt;!-- language: lang-js --&gt;

    function check(str){
      if(!(str.length &amp;&amp; str.length - 1)) return false;
      let temp = &#39;&#39;;
      for(let i = 0;i&lt;=str.length/2;i++){
        temp += str[i]
        //console.log(str.replace(new RegExp(temp,&quot;g&quot;),&#39;&#39;))
        if(!str.replace(new RegExp(temp,&quot;g&quot;),&#39;&#39;)) return true;
      }
      return false;
    }

    console.log(check(&#39;aa&#39;)) //true
    console.log(check(&#39;aaa&#39;)) //true
    console.log(check(&#39;abcabcabc&#39;)) //true
    console.log(check(&#39;aba&#39;)) //false
    console.log(check(&#39;ababa&#39;)) //false

&lt;!-- end snippet --&gt;

Checking of this is part of the real problem. I can&#39;t afford a non-efficient solution like this. First of all, it&#39;s looping through half of the string.

The second problem is that it is using `replace()` in each loop which makes it slow. Is there a better solution regarding performance?


How do I check if a string is entirely made of the same substring?

Surprisingly, the following code outputs:
```none
/
-1
```
The code:
```
public class LoopOutPut {

    public static void main(String[] args) {
        LoopOutPut loopOutPut = new LoopOutPut();
        for (int i = 0; i &lt; 30000; i++) {
            loopOutPut.test();
        }

    }

    public void test() {
        int i = 8;
        while ((i -= 3) &gt; 0) ;
        String value = i + &quot;&quot;;
        if (!value.equals(&quot;-1&quot;)) {
            System.out.println(value);
            System.out.println(i);
        }
    }

}
```

I tried many times to determine how many times this would occur, but, unfortunately, it was ultimately uncertain, and I found that the output of -2 sometimes turned into a period. In addition, I also tried to remove the while loop and output -1 without any problems. Who can tell me why?

----------------------------------

JDK version information:
```none
HopSpot 64-Bit 1.8.0.171
IDEA 2019.1.1
```

The output -1 becomes a slash in the loop

Worth a thousand words:

    #include&lt;string&gt;
    #include&lt;iostream&gt;
    
    class SayWhat {
        public:
        SayWhat&amp; operator[](const std::string&amp; s) {
            std::cout &lt;&lt; s &lt;&lt; &quot;\n&quot;;
            return *this;
        }
    };
    
    int main() {
        SayWhat ohNo;
        // ohNo[1]; // Does not compile. Logic prevails.
        ohNo[0]; // you didn&#39;t! this compiles.
        return 0;
    }

The compiler is not complaining when passing the number 0 to the bracket operator accepting a string. Instead, this compiles and fails before entry to the method with:

    terminate called after throwing an instance of &#39;std::logic_error&#39;
      what():  basic_string::_S_construct null not valid

For reference:

    &gt; g++ -std=c++17 -O3 -Wall -Werror -pedantic test.cpp -o test &amp;&amp; ./test
    &gt; g++ --version
    gcc version 7.3.1 20180303 (Red Hat 7.3.1-5) (GCC)

**My guess**

The compiler is implicitly using the `std::string(0)` constructor to enter the method, which yields the same  problem (google the above error) for no good reason.

**Question**

Is there anyway to fix this on the class side, so the API user does not feel this and the error is detected at compile time? 

That is, adding an overload

    void operator[](size_t t) {
        throw std::runtime_error(&quot;don&#39;t&quot;);
    }

is not a good solution.



Prevent function taking const std::string&amp; from accepting 0

[f-Strings][1] are available from Python 3.6 and are very useful for formatting strings:

    &gt;&gt;&gt; n=&#39;you&#39;
    &gt;&gt;&gt; f&#39;hello {n}, how are you?&#39;
    &#39;hello you, how are you?&#39;

Reading more about them in [Python 3&#39;s f-Strings: An Improved String Formatting Syntax (Guide)][2]. I found an interesting pattern:

&gt; Note that using triple braces will result in there being only single braces in your string:

&gt;     &gt;&gt;&gt; f&quot;{{{74}}}&quot;
    &#39;{74}&#39;

&gt; However, you can get more braces to show if you use more than triple braces:

&gt;     &gt;&gt;&gt; f&quot;{{{{74}}}}&quot;
    &#39;{{74}}&#39;

And this is exactly the case:

    &gt;&gt;&gt; f&#39;{74}&#39;
    &#39;74&#39;

    &gt;&gt;&gt; f&#39;{{74}}&#39;
    &#39;{74}&#39;

Now if we pass from two `{` to three, the result is the same:

    &gt;&gt;&gt; f&#39;{{{74}}}&#39;
    &#39;{74}&#39;           # same as f&#39;{{74}}&#39; !

So we need up to 4! (`{{{{`) to get two braces as an output:

    &gt;&gt;&gt; f&#39;{{{{74}}}}&#39;
    &#39;{{74}}&#39;

Why is this? What happens with two braces to have Python require an extra one from that moment on?

  [1]: https://www.python.org/dev/peps/pep-0498/
  [2]: https://realpython.com/python-f-strings/





Why is f&#39;{{{74}}}&#39; the same as f&#39;{{74}}&#39; with f-Strings?

I&#39;ve started learning Python recently and I don&#39;t understand why Python behaves like this:

&lt;pre&gt;
&gt;&gt;&gt; &quot;OK&quot;
&#39;OK&#39;
&gt;&gt;&gt; &quot;&quot;&quot;OK&quot;&quot;&quot;
&#39;OK&#39;
&gt;&gt;&gt; &quot;not Ok&#39;
  File &quot;&amp;lt;stdin&amp;gt;&quot;, line 1
    &quot;not Ok&#39;
           ^
SyntaxError: EOL while scanning string literal
&gt;&gt;&gt; &quot;not OK&quot;&quot;&quot;
&#39;not OK&#39;
&lt;/pre&gt;

Why doesn&#39;t it give an error for the last statement as the number of quotes does not match?

Why doesn&#39;t Python give any error when quotes around a string do not match?

the following code works perfectly fine in a Java 1.8 VM but produces a `LambdaConversionException` when executed in a Java 11 VM. Wheres the difference and why does it behave like this?

---
Code:
--

&lt;!-- language: lang-java --&gt;

    public void addSomeListener(Component comp){
        if(comp instanceof HasValue) {
            ((HasValue&lt;?,?&gt;) comp).addValueChangeListener(evt -&gt; {
                //do sth with evt
            });
        }
    }

[HasValue Javadoc][1]

Exception (V11 only):
--

&lt;!-- language: lang-none --&gt;

    Caused by: java.lang.invoke.LambdaConversionException: Type mismatch
    for instantiated parameter 0: class java.lang.Object is not a subtype
    of interface com.vaadin.flow.component.HasValue$ValueChangeEvent
    	at java.base/java.lang.invoke.AbstractValidatingLambdaMetafactory.checkDescriptor(AbstractValidatingLambdaMetafactory.java:308)
     	at java.base/java.lang.invoke.AbstractValidatingLambdaMetafactory.validateMetafactoryArgs(AbstractValidatingLambdaMetafactory.java:294)
     	at java.base/java.lang.invoke.LambdaMetafactory.altMetafactory(LambdaMetafactory.java:503)
     	at java.base/java.lang.invoke.BootstrapMethodInvoker.invoke(BootstrapMethodInvoker.java:138)
    	... 73 more

---
Workaround:
-

    ValueChangeListener&lt;ValueChangeEvent&lt;?&gt;&gt; listener = evt -&gt; {
        // do sth with evt
    };
    ((HasValue&lt;?,?&gt;) comp).addValueChangeListener(listener);

---
System:&lt;br&gt;
OS: Windows 10&lt;br&gt;
IDE: Eclipse 2018-12 (4.10.0)&lt;br&gt;
Java (Compile): ecj&lt;br&gt;
Java (Webserver): JDK 11.0.2&lt;br&gt;
Webserver: Wildfly 15&lt;br&gt;

  [1]: https://demo.vaadin.com/javadoc/com.vaadin/vaadin-core/10.0.3/com/vaadin/flow/component/HasValue.html




Java Casting: Java 11 throws LambdaConversionException while 1.8 does not

Installing `java8` with Homebrew seems to no longer be working. After running:

```
brew install caskroom/cask/java8
```

I get the following error:

```
Error: Cask &#39;java8&#39; is unavailable: &#39;/usr/local/Homebrew/Library/Taps/caskroom/homebrew-cask/Casks/java8.rb&#39; does not exist.
```

Simply doing:

```
brew cask install java8
```

Errors out with:

```
Error: Cask &#39;java8&#39; is unavailable: No Cask with this name exists.
```

This seems like a recent development because I remember installing it this way a few months ago. Any suggestions on how to properly install `java8` on MacOS nowadays?



Unable to install java8 with homebrew

It seems Debian does not support openjdk-8-jdk anymore due to a security issue. What is the easiest way to install openjdk-8-jdk for Debian 10 (Buster)?

How to install openjdk-8-jdk on Debian 10 (Buster)?

While I was in a dockerization project in my current job, I got this doubt: Which Java can I use?

This doubt is due to :

![java download alert](https://raw.githubusercontent.com/jrichardsz/static_resources/master/java/java-8-license-change-red-warning-alert.png)

So after some researches I got these conclusions:

- Since the Java 8 update at **April 16, 2019 8u221**, all versions and updates for (Java 8, 9, 10, 11 and 13) has no cost **just** for **personal use and development purposes**. Any other use, needs a **Commercial License**
- Legacy versions prior to 7, does not have and will not have any update. Maybe a sales contact could be a solution if an update in these versions are required for Legacy Systems Support.
- If I want to use Java 8 oracle version for **commercials purposes** and **FREE**, I need to use a previous version of **April 16, 2019 8u221 update**

---

# Questions

According to my conclusions:

- If my development strictly needs or was developed with **JDK 8**, Can I only use Oracle Java SE 8 [JDK 8u202 and earlier versions](https://www.oracle.com/technetwork/java/javase/downloads/java-archive-javase8-2177648.html?printOnly=1) for **FREE** and **commercial purposes** accepting issues and security problems?

- If I can change my development **and** I want still **FREE**, **and** I want to have improvements and security updates, I must use one of these  [java open implementations](https://gist.github.com/jrichardsz/83db09163ca9a0db4c9cd4f91cbf0598)?

---
# References

- [End of Public Updates for Oracle JDK 8](https://www.oracle.com/technetwork/java/java-se-support-roadmap.html)
- [The Oracle JDK License has changed for releases starting April 16, 2019.](https://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html)
- [Official List of updates and release versions](https://www.oracle.com/technetwork/java/javase/8u-relnotes-2225394.html)
- [Java official supported versions](https://www.oracle.com/technetwork/java/javase/downloads/index.html)
- [Oracle Java 8 download alert](https://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html)
- [Oracle Java 8 unsupported but free version](https://www.oracle.com/technetwork/java/javase/downloads/java-archive-javase8-2177648.html?printOnly=1)
- [Java 4 legacy official download page](https://www.oracle.com/java/technologies/java-archive-javase-v14-downloads.html)
- [Java 5 legacy official download page](https://www.oracle.com/java/technologies/java-archive-javase5-downloads.html)
- [Java 6 legacy official download page](https://www.oracle.com/java/technologies/javase-java-archive-javase6-downloads.html)
- [Java 7 legacy official download page](https://www.oracle.com/technetwork/java/javase/downloads/java-archive-downloads-javase7-521261.html)

Which free version of Java can I use for production environments and or commercial purposes?

While trying out the *multi-catch* feature I found in my `m1()` method everything is working fine as expected.

However, in `m2()` the same code does not compile. I have just changed the syntax to reduce the number of lines of code.
    
    public class Main {
    
        public int m1(boolean bool) {
            try {
                if (bool) {
                    throw new Excep1();
                }
                throw new Excep2();
                //This m1() is compiling  abs fine.
            } catch (Excep1 | Excep2 e) {
                return 0;
            }
        }
    
        public int m2(boolean b) {
            try {
                throw b ? new Excep1() : new Excep2();
                //This one is not compiling.
            } catch (Excep1 | Excep2 e) {
                return 0;
            }
        }
    
        private static interface I {
        }
    
        private static class Excep1 extends Exception implements I {
        }
    
        private static class Excep2 extends Exception implements I {
        }
    }

Why doesn&#39;t method `m2()` compile?


Content Type	Original Author	Original Content on Stackoverflow
Question	Fuyang Liu	View Question on Stackoverflow
Solution 1 - Java	Karol Dowbecki	View Answer on Stackoverflow

Why does String.replaceAll() work differently in Java 8 from Java 9?

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componentWillReceiveProps, componentDidUpdate for React Hook

Error response from daemon: Dockerfile parse error Unknown flag: mount

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