Is there any way to detect if there 's an JRE installed on customer machine

Question

I want to know if the customer has the JRE installed to make sure that my program can run.So the problem come,how can I know that.Someone told me to use
a command like "java -version",which seemed reasonable.In that way,i should write a bat file do that.This file will detect if there is an JRE installed,if there is get the version of the JRE and compare with the available JRE of my program,but if not,connect to the offical site to download.It is really hard for me to do that bat file.I am just a new programer without any experience.So I really appreciate if someone give me some advice.Sorry,my english is so bad.I am waithing for the help.

Answer 1

scphan wrote:
masijade. wrote:
P.S. @OP, java -version will only work if the path is set correctly, of course, and what it returns will not, necessarily, be the highest version installed on the system, just the particular version that the path points to first.>This works in versions 1.1 and up:
public class FindVersion
     public static void main( String args[] )
          String prop = System.getProperty( "java.version" );
          System.out.println( prop );
import java.io.*;
public class ReadVersion
     public static void main( String args[] )
          try
               Process proc = Runtime.getRuntime().exec( "java FindVersion" );
               BufferedReader in = new BufferedReader(new InputStreamReader(proc.getInputStream()));
               String line = in.readLine();
               System.out.println( "java.version="+line );
          catch ( IOException e )
               e.printStackTrace();
Yes, of course that does, when Java is already installed, of course. The question here was how to determine if it is installed, at all. And, that will also only give you the version of the Java currently being used, of course, and not, as I pointed out in that quoted post, not necessarily the highest version installed on the system.
Please make your posts applicable.