Restructures demos.

demos/java/src/app/TextData.java

@@ -0,0 +1,18 @@
+package app;
+
+public class TextData extends ExtractedData {
+    private final String textValue;
+
+    public TextData(String text) {
+        this.textValue = text;
+    }
+
+    @Override
+    protected String[] getTags() {
+        return new String[] { "text" };
+    }
+
+    public String getText() {
+        return this.textValue;
+    }
+}