This is my JDK switcher script. Assumes bash. You should probably use something like SDKMAN! instead.

jdk.sh

#!/bin/bash
# https://gist.github.com/wmono/3b19e6613fb0e8abd798f0644d96c4aa

JDK_PREFIX="${JDK_PREFIX:-$HOME/local}"

###############################################################################

request="$1"
changed_jdk=0

(return 0 2>/dev/null) && was_sourced=1 || was_sourced=0

use_jdk() {
	local find_names
	build_find_names find_names "$@"
	local new_home="$(find "$JDK_PREFIX" -maxdepth 1 -type d,l -a \( "${find_names[@]}" \) 2>/dev/null | sort -n | tail -1)"
	if [ -n "$new_home" -a -x "$new_home/bin/java" ]; then
		export JAVA_HOME="$new_home"
		export PATH="$JAVA_HOME/bin:$PATH"
		changed_jdk=1
		java -version
	else
		echo "Cannot find JAVA_HOME for $request in $JDK_PREFIX" >&2
		if [ "$was_sourced" -eq 0 ]; then exit 1; fi
	fi
}

build_find_names() {
	local -n result="$1"
	shift
	result+=( '-name' "$1" )
	shift
	while [ -n "$1" ]; do
		result+=( '-o' '-name' "$1" )
		shift
	done
}


case $request in
	"")
		java -version
		if [ "$was_sourced" -eq 0 ]; then exit 1; fi
		;;
	6|7|8)
		use_jdk "jdk${request}u*" "jdk1.${request}.*"
		;;
	*)
		use_jdk "jdk-$request.*"
		;;
esac


if [ "$was_sourced" -eq 0 -a "$changed_jdk" -eq 1 ]; then
	echo
	echo '*** Starting new shell ***'
	exec "$SHELL"
fi