javahome

#!/bin/bash

javahome() {
	# Check for a valid operating system

	local BASE_JAVA=
	local JAVA_VERSION=$1

	if [ -d /usr/java ]; then
		BASE_JAVA=/usr/java
	elif [ -d /usr/lib/jvm ]; then
		BASE_JAVA=/usr/lib/jvm
	else
		echo "Unable to change Java on your operating system"
		return 0
	fi

	# If this is diagnostic, just report JAVA_HOME

	if [ "" == "${JAVA_VERSION}" ]; then
		if [ "" != "${JAVA_HOME}" ]; then
			echo JAVA_HOME=$JAVA_HOME
			$JAVA_HOME/bin/java 2>&1 -version | head -1
			return 0
		fi

		JAVA_VERSION=8
	fi

	# Remove the existing JAVA_HOME from the path

	if [ "" != "$JAVA_HOME" ]; then
		export PATH=$(echo $PATH | sed -e "s;:$JAVA_HOME/bin;;g" | sed -e "s;$JAVA_HOME/bin:;;g")
	fi

	# Check for a valid /etc/alternatives value

	local ALT_ID=

	# Choose the closest matching version

	for folder in $(ls -1 ${BASE_JAVA} | grep -F "jdk1.${JAVA_VERSION}.0" | sort -t'_' -k2nr); do
		if [ ! -f $BASE_JAVA/$folder/bin/java ]; then
			continue
		fi

		ALT_ID=$BASE_JAVA/$folder
		break
	done

	# If we couldn't find one, maybe they installed it through a package manager

	if [ "" == "$ALT_ID" ]; then
		for folder in $(ls -1 ${BASE_JAVA} | grep -F java-${JAVA_VERSION}-oracle); do
			if [ ! -f $BASE_JAVA/$folder/bin/java ]; then
				continue
			fi

			ALT_ID=$BASE_JAVA/$folder
			break
		done
	fi

	if [ "" == "$ALT_ID" ]; then
		for folder in $(ls -1 ${BASE_JAVA} | grep -F java-${JAVA_VERSION}-openjdk); do
			if [ ! -f $BASE_JAVA/$folder/bin/java ]; then
				continue
			fi

			ALT_ID=$BASE_JAVA/$folder
			break
		done
	fi

	# If we still couldn't find it, report that Java could not be found

	if [ "" == "$ALT_ID" ]; then
		echo "Unable to find Java ${JAVA_VERSION}"
		return 1
	fi

	export JAVA_HOME=$ALT_ID

	# Prepend Java to the path

	echo JAVA_HOME=$JAVA_HOME
	$JAVA_HOME/bin/java 2>&1 -version | head -1
	export PATH=$JAVA_HOME/bin:$PATH
}

javahome $@