diff --git a/java/append_primes/Main.java b/java/append_primes/Main.java
index 962d515..3ab99c0 100644
--- a/java/append_primes/Main.java
+++ b/java/append_primes/Main.java
@@ -6,14 +6,8 @@ public class Main
     {
         Util.init();
 
-        ArrayList<Long> vals = new ArrayList<Long>();
-        vals.add(2l);
-        vals.add(3l);
-        vals.add(5l);
-        vals.add(7l);
-
-        Tree tree = new Tree(0, vals);
-        for (int i = 0; i < 20; i++) {
+        Tree tree = new Tree(0, new ArrayList<Long>());
+        for (int i = 0; i < 9; i++) {
             tree.step();
             Util.printList(tree.longestPath());
         }
diff --git a/java/append_primes/Util.java b/java/append_primes/Util.java
index e6cb428..a400834 100644
--- a/java/append_primes/Util.java
+++ b/java/append_primes/Util.java
@@ -17,6 +17,10 @@ class Util
         if (primes.containsKey(val)) {
             return primes.get(val);
         }
+        if (val < 2) {
+            primes.put(val, false);
+            return false;
+        }
         for (int i = 2; i * i <= val; i++) {
             if (val % i == 0) {
                 primes.put(val, false);
diff --git a/java/template/Util.java b/java/template/Util.java
index 5e80476..80404f5 100644
--- a/java/template/Util.java
+++ b/java/template/Util.java
@@ -21,6 +21,10 @@ class Util
         if (primes.containsKey(val)) {
             return primes.get(val);
         }
+        if (val < 2) {
+            primes.put(val, false);
+            return false;
+        }
         for (int i = 2; i * i <= val; i++) {
             if (val % i == 0) {
                 primes.put(val, false);