> Could not find tools.jar. Please check that /Library/Internet Plug-Ins/JavaAppletPlugin.plugin/Contents/Home contains a valid JDK installation. code example

Example 1: Could not find tools.jar. Please check that

On my system (Win 10, JRE 1.8.0, Android Studio 3.1.2, Gradle 4.1) there is no 
tools.jar in the JRE directory (C:\Program Files\Java\jre1.8.0_171).

However, I found it in C:\Program Files\Android\Android Studio\jre\lib and 
tried setting JAVA_HOME=C:\Program Files\Android\Android Studio\jre

That works (for me)!

Example 2: ionic Please check that /Library/Internet Plug-Ins/JavaAppletPlugin.plugin/Contents/Home contains a valid JDK installation.

export JAVA_HOME=/Library/Java/JavaVirtualMachines/jdk1.8.0_91.jdk/Contents/Home