Anchor the -java match pattern at the end of the string. (#16626)

This fixes the offline install problem of the logstash-input-java_filter_example off-line install.

lib/pluginmanager/pack_installer/pack.rb

@@ -39,7 +39,7 @@ class Pack
     class GemInformation
       EXTENSION = ".gem"
       SPLIT_CHAR = "-"
-      JAVA_PLATFORM_RE = /-java/
+      JAVA_PLATFORM_RE = /-java$/
       DEPENDENCIES_DIR_RE = /dependencies/
 
       attr_reader :file, :name, :version, :platform

spec/unit/plugin_manager/pack_installer/pack_spec.rb

@@ -113,4 +113,24 @@
       expect(subject.plugin?).to be_falsey
     end
   end
+
+  context "when it is Java plugin example from an offline zip file" do
+    let(:gem) { "/tmp/randomValue/randomValue2/logstash/logstash-filter-java_filter_example-1.0.5.gem"}
+
+    it "#dependency? return false" do
+      expect(subject.dependency?).to be_falsey
+    end
+
+    it "#plugin? return true" do
+      expect(subject.plugin?).to be_truthy
+    end
+
+    it "returns the version" do
+      expect(subject.version).to eq("1.0.5")
+    end
+
+    it "returns the name" do
+      expect(subject.name).to eq("logstash-filter-java_filter_example")
+    end
+  end
 end