extras: add P16-P23, P25

Signed-off-by: Amneesh Singh <natto@weirdnatto.in>

P25.java

@@ -0,0 +1,25 @@
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+public class P25 {
+    public static void main(String[] args) {
+        List<String> names = new ArrayList<>();
+        
+        names.add("Batu");
+        names.add("Amba");
+        names.add("John");
+        names.add("Quandangle");
+        names.add("Harikrishan");
+        
+        System.out.println("Names before sorting:");
+        for (String name : names)
+            System.out.print(name + " ");
+        
+        Collections.sort(names);
+        
+        System.out.println("\nNames after sorting:");
+        for (String name : names)
+            System.out.print(name + " ");
+    }
+}