以编程方式检查我的系统上是否安装了Java7(Jre7)或更高版本

 ```python

 import os

 import subprocess

 def check_java_version():

     try:

         java_path = os.environ.get('JAVA_HOME')

         if java_path:

             java_executable = os.path.join(java_path, 'bin', 'java')

             output = subprocess.check_output([java_executable, '-version'], stderr=subprocess.STDOUT)

             version_line = output.splitlines()[0].decode('utf-8')

             version = version_line.split()[2].strip('"')

             return version

         else:

             return "Java is not installed."

     except subprocess.CalledProcessError:

         return "Java is not installed."

 print(check_java_version())

 ```

 ```java

 public class CheckJavaVersion {

     public static void main(String[] args) {

         String javaHome = System.getenv("JAVA_HOME");

         if (javaHome != null) {

             String javaExecutable = javaHome + "/bin/java";

             try {

                 Process process = Runtime.getRuntime().exec(new String[]{javaExecutable, "-version"});

                 BufferedReader reader = new BufferedReader(new InputStreamReader(process.getErrorStream()));

                 String versionLine = reader.readLine();

                 String version = versionLine.split(" ")[2].replace("\"", "");

                 System.out.println(version);

             } catch (IOException e) {

                 System.out.println("Java is not installed.");

             }

         } else {

             System.out.println("Java is not installed.");

         }

     }

 }

 ```