Simplify the Java Knapsack example, so it is easier for LLMs to solve

Part of #230

testdata/java/light/src/main/java/com/eval/Knapsack.java

@@ -1,33 +1,33 @@
 package com.eval;
 
 public class Knapsack {
-  static int maximumValue(int maximumWeight, Item[] items) {
-    int[][] knapsack = new int[items.length + 1][maximumWeight + 1];
-    for (int item = 0; item <= items.length; item++) {
+  static int maximumValue(int maximumWeight, int[] weights, int[] values) {
+    if (weights.length != values.length) {
+      throw new IllegalArgumentException("the arrays must have the same length");
+    }
+    int numberOfItems = weights.length;
+
+    int[][] knapsack = new int[numberOfItems + 1][maximumWeight + 1];
+    for (int item = 0; item <= numberOfItems; item++) {
       for (int weight = 0; weight <= maximumWeight; weight++) {
         knapsack[item][weight] = 0; // Return 0 if not filled
       }
     }
-    for (int item = 0; item <= items.length; item++) {
+    for (int item = 0; item <= numberOfItems; item++) {
       for (int weight = 0; weight <= maximumWeight; weight++) {
         if (item == 0 || weight == 0) {
           knapsack[item][weight] = 0;
-        } else if (items[item - 1].weight > weight) {
+        } else if (weights[item - 1] > weight) {
           knapsack[item][weight] = knapsack[item - 1][weight];
         } else {
-          int itemValue = items[item - 1].value;
-          int itemWeight = items[item - 1].weight;
-          knapsack[item][weight] =
-              Math.max(itemValue + knapsack[item - 1][weight - itemWeight],
-                       knapsack[item - 1][weight]);
+          int itemValue = values[item - 1];
+          int itemWeight = weights[item - 1];
+          knapsack[item][weight] = Math.max(itemValue + knapsack[item - 1][weight - itemWeight],
+              knapsack[item - 1][weight]);
         }
       }
     }
-    return knapsack[items.length][maximumWeight];
-  }
 
-  class Item {
-    int weight;
-    int value;
+    return knapsack[numberOfItems][maximumWeight];
   }
 }