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<p>This sample should make the reader aware, that it is useful and
helpful to use plain Java programs, commands with an installed
JRE, without any need for any special configuration. <br>
</p>
<p>Once Java/JDK gets installed globally all processes have access
to the appropriate "Java/JDK runtime environment (JRE)".</p>
<p>A globally installed JRE can be exploited in many ways. <br>
</p>
<p>One way, following the important property of Java's "once
compiled, run everyhwere" and the excellent support of Java class
libraries to abstract operating system dependent functionality in
a portable manner it is very attractive to exploit Java/JDK in
form of Java commands.</p>
<p>Here is a simple command that will list all installed font
families on any computer, no matter whether it is Windows, Linux
or macOS. As the font family names are output to standard output
such a Java program can be exploited in pipes making it easy to
use Java commands in shell programs.</p>
<p>Here the Java program ListFonts.java</p>
<blockquote>
<p>import java.awt.*;<br>
<br>
// demonstrate a simple Java command tool to list fonts
available on the<br>
// user's platform to stdout to allow e..g integration with
pipes<br>
public class ListFonts<br>
{<br>
public static void main (String args[])<br>
{<br>
listFonts();<br>
}<br>
<br>
// list font names to stdout: allows for making it available
for piping<br>
public static void listFonts ()<br>
{<br>
for (String fn :
GraphicsEnvironment.getLocalGraphicsEnvironment().getAvailableFontFamilyNames())<br>
{<br>
System.out.println(fn);<br>
}<br>
}<br>
}<br>
</p>
</blockquote>
<p>As simple as this Java program seems, it is an incredible time
saver compared to programs in other programming languages! <br>
</p>
<p>The reason being simple: you compile that program once and can
use it unchanged on all operating systems like Windows, Linux and
macOS, via the JRE with its standard runtime Java class libraries.</p>
<p>It is a command that is easy to use, no configuration whatsoever
necessary.<br>
</p>
<p>On my Windows machine the output of running:</p>
<blockquote>
<p>java ListFonts<br>
</p>
</blockquote>
<p>is something like:</p>
<blockquote>
<p>Arial<br>
Arial Black<br>
Arial Narrow<br>
Arial Rounded MT Bold<br>
Bahnschrift<br>
Baskerville Old Face<br>
Bauhaus 93<br>
... cut ...<br>
Wingdings<br>
Wingdings 2<br>
Wingdings 3<br>
Yu Gothic<br>
Yu Gothic Light<br>
Yu Gothic Medium<br>
Yu Gothic UI<br>
Yu Gothic UI Light<br>
Yu Gothic UI Semibold<br>
Yu Gothic UI Semilight<br>
ZWAdobeF<br>
</p>
</blockquote>
<p>---<br>
</p>
<p>As this is a Java command that writes to stdout one can use it in
a little script, e.g. to learn which "Gothic" fonts are installed
on a particular machine:</p>
<p>On my Windows machine the output of running:</p>
<blockquote>
<p>java ListFonts | grep -i gothic<br>
</p>
</blockquote>
<p> is:</p>
<blockquote>
<p>Century Gothic<br>
Copperplate Gothic Bold<br>
Copperplate Gothic Light<br>
Franklin Gothic Book<br>
Franklin Gothic Demi<br>
Franklin Gothic Demi Cond<br>
Franklin Gothic Heavy<br>
Franklin Gothic Medium<br>
Franklin Gothic Medium Cond<br>
Malgun Gothic<br>
Malgun Gothic Semilight<br>
Microsoft NeoGothic<br>
MS Gothic<br>
MS PGothic<br>
MS UI Gothic<br>
Showcard Gothic<br>
Yu Gothic<br>
Yu Gothic Light<br>
Yu Gothic Medium<br>
Yu Gothic UI<br>
Yu Gothic UI Light<br>
Yu Gothic UI Semibold<br>
Yu Gothic UI Semilight<br>
</p>
</blockquote>
<p>---</p>
<p>There are (even quite complex) Java programs that can serve as
commands and used in pipes making it easy to exploit the
functionality of the Java class libraries contained in the JRE on
all operating system platforms. It is easy because it is easy to
launch the Java programs as the JRE is available. <br>
</p>
<p>If the JRE gets updated by installing a bugfix or a newer
Java/JDK all of the existing Java programs keep on running
unchanged and uninterrupted.<br>
</p>
<p>It is easy to exploit Java in this manner and has been done for
decades. <br>
</p>
---rony
<p><br>
</p>
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