ninja: error: loading 'build.ninja': The system cannot find the file specified. code example

Example 1: python wifi moudel [WinError 2] The system cannot find the file specified

#Here it is
from wifi import Cell, Scheme
Cell.all('wlan0')
cell = Cell.all('wlan0')[0]
scheme = Scheme.for_cell('wlan0', 'home', cell, passkey)
scheme.save()
scheme.activate()

scheme = Scheme.find('wlan0', 'home')
scheme.activate()

Example 2: Error executing Maven. java.io.FileNotFoundException: The specified user settings file does not exist: /etc/java-8-openjdk

JAVA_HOME=/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.141-3.b16.el6_9.x86_64

Example 3: [ERROR] Error executing Maven. java.io.FileNotFoundException: The specified user settings file does not exist: /usr/lib/jvm/java-1.8.0-openjdk-amd64

<plugin>
    <artifactId>maven-compiler-plugin</artifactId>
    <version>3.7.0</version>
    <configuration>
        <fork>true</fork>
        <executable>/usr/lib/jvm/java-11-openjdk-amd64/bin/javac</executable>
    </configuration>
</plugin>