Recursive implementation, with nastiness.

Knapsack.java

import java.util.Arrays;
import java.util.List;

public class Knapsack {

    private int[][] valueTable;
    private List<Item> items;

    int maximumValue(int capacity, List<Item> items) {
        valueTable = new int[items.size() + 1][capacity + 1];
        this.items = items;
        for (int[] row: valueTable) {
            Arrays.fill(row, -1);
        }
        return maxValueInRange(items.size(), capacity);
    }

    private int maxValueInRange(int i, int j) {
        if (i == 0 || j <= 0) {
            return 0;
        }
        if (valueTable[i - 1][j] == -1) {
            valueTable[i - 1][j] = maxValueInRange(i - 1, j);
        }
        if (items.get(i - 1).weight > j) {
            valueTable[i][j] = valueTable[i - 1][j];
        } else {
            if (valueTable[i - 1][j - items.get(i - 1).weight] == -1) {
                valueTable[i - 1][j - items.get(i - 1).weight] =
                       maxValueInRange(i - 1, j - items.get(i - 1).weight);
            }
            valueTable[i][j] =
                    Math.max(valueTable[i - 1][j],
                    valueTable[i - 1][j - items.get(i - 1).weight] +
                            items.get(i - 1).value);
        }
        return valueTable[i][j];
    }

}