Restructures demos.

demos/java/src/app/ExtractedData.java

@@ -0,0 +1,31 @@
+package app;
+
+import java.util.HashMap;
+
+import com.fasterxml.jackson.annotation.JsonIgnore;
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.ObjectMapper;
+
+public abstract class ExtractedData {
+    public HashMap<String, Boolean> getKind() {
+        HashMap<String, Boolean> m = new HashMap<>();
+        for (String s : getTags()) {
+            m.put(s, true);
+        }
+        return m;
+    }
+
+    @JsonIgnore
+    protected abstract String[] getTags();
+
+    @Override
+    public String toString() {
+        ObjectMapper objectMapper = new ObjectMapper();
+        try {
+            String val = objectMapper.writeValueAsString(this);
+            return val;
+        } catch (JsonProcessingException e) {
+            return "JsonProcessingException";
+        }
+    }
+}