Note to self: Updated usejava BASH function for MacOSX

For use when you have multiple JVM providers (Apple & Oracle), you want to be able to switch between JDKs for each CLI

usejava ()
{
    local sel=$1.jdk
    if [ -x "/Library/Java/JavaVirtualMachines/jdk$sel/Contents/Home/bin/java" -a ! -x "/Library/Java/JavaVirtualMachines/$1/Contents/Home/bin/java" ]
    then
        sel=jdk$sel
    fi
    local base=/Library/Java/JavaVirtualMachines
    if [ -x "/System/Library/Java/JavaVirtualMachines/$sel/Contents/Home/bin/java" ]
    then
        base=/System/Library/Java/JavaVirtualMachines
    fi

    if [ -z "$1" -o ! -x "$base/$sel/Contents/Home/bin/java" ]
    then
        local prefix="Syntax: usejava "
        for i in /Library/Java/JavaVirtualMachines/* /System/Library/Java/JavaVirtualMachines/*
        do
            if [ -x "$i/Contents/Home/bin/java" ]
            then
                /bin/echo -n "$prefix$(basename $i | sed -e "s/^jdk//;s/\.jdk$//;")"
                prefix=" | "
            fi
        done
        /bin/echo ""
    else
        if [ -z "$JAVA_HOME" ]
        then
            export PATH=$base/$sel/Contents/Home/bin:$PATH
        else
            export PATH=$(echo $PATH|sed -e "s:$JAVA_HOME/bin:$base/$sel/Contents/Home/bin:g")
        fi
        export JAVA_HOME=$base/$sel/Contents/Home
        echo -n -e "\033]0;$(java -version 2>&1 | sed -e "s/.*\"\(.*\)\".*/Java \1/;q")\007"
    fi
}

There is additional fun to be had, given that most Java based launchers that try to fix JAVA_HOME when not set will guess the Apple JVM path… so the following Java program can help

public class FixJavaHome {
  public static void main(String[] args) {
  	String javaHome = System.getProperty("java.home");
  	if (javaHome.endsWith("/jre")) {
  		javaHome = javaHome.substring(0,javaHome.length() - "/jre".length());
  	}
    System.out.println("export JAVA_HOME=\""+javaHome+'\"');
  }
}

Install like so

mkdir -p ~/bin/FixJavaHome && cd ~/bin/FixJavaHome && cat > FixJavaHome.java <<EOF
public class FixJavaHome {
  public static void main(String[] args) {
  	String javaHome = System.getProperty("java.home");
  	if (javaHome.endsWith("/jre")) {
  		javaHome = javaHome.substring(0,javaHome.length() - "/jre".length());
  	}
    System.out.println("export JAVA_HOME=\""+javaHome+'\"');
  }
}
EOF
javac FixJavaHome.java
cd -

If you add the following to your ~/.bash_profile

eval $(java -cp ~/bin/FixJavaHome/ FixJavaHome)
echo -n -e "\033]0;$(java -version 2>&1 | sed -e "s/.*\"\(.*\)\".*/Java \1/;q")\007"

Then your JAVA_HOME should be set up from the start, as well as your Terminal window title