Question: I have a problem with the Arduino code. DFRobotDFPlayerMini library. when you press the button, the music plays, and when you press it again, it pauses. I have music playing 0.5 second then repeats. thank you in advance.

```
#include "SoftwareSerial.h"
#define BTN_PIN 3
#include "Arduino.h"
#include "DFRobotDFPlayerMini.h"

boolean butt_flag = 0;
boolean butt;
boolean pl;
SoftwareSerial mySoftwareSerial(10, 11); // RX, TX
DFRobotDFPlayerMini myDFPlayer;

void setup()
{
    butt = !digitalRead(3);
    mySoftwareSerial.begin(9600);
    Serial.begin(115200);
    if (!myDFPlayer.begin(mySoftwareSerial)) {
        Serial.println(F("Unable to begin:"));
        Serial.println(F("1.Please recheck the connection!"));
        Serial.println(F("2.Please insert the SD card!"));
        while(true){
            delay(0);
        }
    }
    Serial.println(F("DFPlayer Mini online."));
    pl = 0;
    myDFPlayer.volume(30); 
    myDFPlayer.play(1);
}

void loop()
{
    butt = !digitalRead(3);
    if (butt == 1 && butt_flag == 0) {
        butt_flag = 1;
        pl = !pl;
    }
    if (pl = 1)
        myDFPlayer.play();
    else
        myDFPlayer.pause();
}

```

Answer: 
Per @chepner: `/usr/local/bin/mvn` is a symlink to the latest installed version when installed via homebrew.

I changed `export MAVEN_HOME="/usr/local/Cellar/maven/3.6.3/mvn"` to `export MAVEN_HOME="/usr/local/bin/mvn"` in my `~/.zshrc` config and everything is good to go.
I work on windows and i have created folder dev-env and the path of this folder i have added in PATH variable.

I have installed the version of java jdk8, jdk9, jdk11, jdk13.
I have created bat files and place them in dev-env : jdk8.bat ,jdk9.bat, jdk9.bat, jdk11.bat and jdk13.bat.
Inside a bat files I do the switch of version of java.

```
@echo off 
set JAVA_HOME=path to jdk version
set PATH = %JAVA_HOME%\bin+PATH
java -version

```

Same thing in maven . I created different bat files maven3.bat, maven36.bat.

```
@echo off 
set MAVAEN_HOME=path to jdk version
set PATH = %MAVEN_HOME%\bin+PATH
mvn -version

```

So , If i want to switch from one version to another. I open the cmd and the run the bat file that has the version that i want.