Consolidate Java version checking code, fix bugs

where versions are in different forms
Add warning about Java 7

apps/routerconsole/java/src/net/i2p/router/update/NewsFetcher.java

@@ -264,8 +264,8 @@ class NewsFetcher extends UpdateRunner {
                             }
                             String minJava = args.get(MIN_JAVA_VERSION_KEY);
                             if (minJava != null) {
-                                String ourJava = System.getProperty("java.version");
+                                if (!SystemVersion.isJava(minJava)) {
-                                if (VersionComparator.comp(ourJava, minJava) < 0) {
+                                    String ourJava = System.getProperty("java.version");
                                     String msg = _mgr._t("Requires Java version {0} but installed Java version is {1}", minJava, ourJava);
                                     _log.logAlways(Log.WARN, "Cannot update to version " + ver + ": " + msg);
                                     _mgr.notifyVersionConstraint(this, _currentURI, ROUTER_SIGNED, "", ver, msg);

apps/routerconsole/java/src/net/i2p/router/update/PluginUpdateRunner.java

@@ -409,8 +409,7 @@ class PluginUpdateRunner extends UpdateRunner {
             }
 
             minVersion = PluginStarter.stripHTML(props, "min-java-version");
-            if (minVersion != null &&
+            if (minVersion != null && !SystemVersion.isJava(minVersion)) {
-                VersionComparator.comp(System.getProperty("java.version"), minVersion) < 0) {
                 to.delete();
                 statusDone("<b>" + _t("This plugin requires Java version {0} or higher", minVersion) + "</b>");
                 return;

apps/routerconsole/java/src/net/i2p/router/web/PluginStarter.java

@@ -358,8 +358,7 @@ public class PluginStarter implements Runnable {
         }
 
         minVersion = stripHTML(props, "min-java-version");
-        if (minVersion != null &&
+        if (minVersion != null && !SystemVersion.isJava(minVersion)) {
-            VersionComparator.comp(System.getProperty("java.version"), minVersion) < 0) {
             String foo = "Plugin " + appName + " requires Java version " + minVersion + " or higher";
             log.error(foo);
             disablePlugin(appName);

apps/routerconsole/java/src/net/i2p/router/web/RouterConsoleRunner.java

@@ -340,13 +340,13 @@ public class RouterConsoleRunner implements RouterApp {
 
     /** @since 0.9.17 */
     private void checkJavaVersion() {
-        boolean noJava7 = !SystemVersion.isJava7();
+        boolean noJava8 = !SystemVersion.isJava8();
         boolean noPack200 = (PluginStarter.pluginsEnabled(_context) || !NewsHelper.isUpdateDisabled(_context)) &&
                             !FileUtil.isPack200Supported();
         boolean openARM = SystemVersion.isARM() && SystemVersion.isOpenJDK() && !SystemVersion.isJava9();
         boolean isZero = SystemVersion.isZeroVM();
         boolean isJava11 = false; // SystemVersion.isJava11();
-        if (noJava7 || noPack200 || openARM || isZero || isJava11) {
+        if (noJava8 || noPack200 || openARM || isZero || isJava11) {
             String s = "Java version: " + System.getProperty("java.version") +
                        " OS: " + System.getProperty("os.name") + ' ' +
                        System.getProperty("os.arch") + ' ' +
@@ -354,8 +354,8 @@ public class RouterConsoleRunner implements RouterApp {
             net.i2p.util.Log log = _context.logManager().getLog(RouterConsoleRunner.class);
             log.logAlways(net.i2p.util.Log.WARN, s);
             System.out.println("Warning: " + s);
-            if (noJava7) {
+            if (noJava8) {
-                s = "Java 7 is now required, please upgrade";
+                s = "Java 8 or higher will be required in a future release, please upgrade Java";
                 log.logAlways(net.i2p.util.Log.WARN, s);
                 System.out.println("Warning: " + s);
             }

core/java/src/net/i2p/util/SystemVersion.java

@@ -243,6 +243,40 @@ public abstract class SystemVersion {
         return _oneDotEleven;
     }
 
+    /**
+     *  Handles Android also
+     *
+     *  @param minVersion e.g. 11
+     *  @return true if greater than or equal to minVersion
+     *  @since 0.9.41
+     */
+    public static boolean isJava(int minVersion) {
+        return isJava("1." + minVersion);
+    }
+
+    /**
+     *  Handles Android, and minVersions in both forms (e.g. 11 or 1.11)
+     *
+     *  @param minVersion either 1.x or x form works
+     *  @return true if greater than or equal to minVersion
+     *  @since 0.9.41
+     */
+    public static boolean isJava(String minVersion) {
+        String version = System.getProperty("java.version");
+        if (!version.startsWith("1."))
+            version = "1." + version;
+        if (!minVersion.startsWith("1."))
+            minVersion = "1." + minVersion;
+        if (_isAndroid) {
+            if (minVersion.startsWith("1.6"))
+                return _oneDotSix;
+            if (minVersion.startsWith("1.7"))
+                return _oneDotSeven;
+            return false;
+        }
+        return VersionComparator.comp(version, minVersion) >= 0;
+    }
+
     /**
      * This isn't always correct.
      * http://stackoverflow.com/questions/807263/how-do-i-detect-which-kind-of-jre-is-installed-32bit-vs-64bit
@@ -342,6 +376,7 @@ public abstract class SystemVersion {
         System.out.println("Java 9   : " + isJava9());
         System.out.println("Java 10  : " + isJava10());
         System.out.println("Java 11  : " + isJava11());
+        System.out.println("Java 12  : " + isJava(12));
         System.out.println("Android  : " + isAndroid());
         if (isAndroid())
             System.out.println("  Version: " + getAndroidVersion());