fix java version parsing

Author: zeitlinger

instrumentation/spring/spring-boot-autoconfigure/src/main/java/io/opentelemetry/instrumentation/spring/autoconfigure/internal/instrumentation/runtimemetrics/Java8RuntimeMetricsProvider.java

@@ -23,7 +23,7 @@ public class Java8RuntimeMetricsProvider implements RuntimeMetricsProvider {
 
   @Override
   public int minJavaVersion() {
-    return 1;
+    return 8;
   }
 
   @Override

instrumentation/spring/spring-boot-autoconfigure/src/main/java/io/opentelemetry/instrumentation/spring/autoconfigure/internal/instrumentation/runtimemetrics/RuntimeMetricsAutoConfiguration.java

@@ -48,7 +48,7 @@ public void handleApplicationReadyEvent(ApplicationReadyEvent event) {
     ConfigPropertiesBridge config =
         new ConfigPropertiesBridge(applicationContext.getBean(ConfigProperties.class));
 
-    double version = Double.parseDouble(System.getProperty("java.specification.version"));
+    double version = javaVersion();
     Optional<RuntimeMetricsProvider> metricsProvider =
         applicationContext.getBeanProvider(RuntimeMetricsProvider.class).stream()
             .sorted(Comparator.comparing(RuntimeMetricsProvider::minJavaVersion).reversed())
@@ -61,4 +61,13 @@ public void handleApplicationReadyEvent(ApplicationReadyEvent event) {
       logger.debug("No runtime metrics instrumentation available for Java {}", version);
     }
   }
+
+  private int javaVersion() {
+    try {
+      return Integer.parseInt(System.getProperty("java.specification.version"));
+    } catch (NumberFormatException nfe) {
+      // The value of the java.specification.version property is 1.8 with a Java 8 runtime.
+      return 8;
+    }
+  }
 }