提供一个贪心算法案例，Java代码

好的，这里给您提供一个贪心算法的经典案例——背包问题，以下是Java代码实现：

public class KnapsackProblem {
    public static int[] greedyKnapsack(int[] wt, int[] val, int capacity) {
        int n = wt.length;

        // calculating the value per unit weight
        double[] ratio = new double[n];
        for (int i = 0; i < n; i++) {
            ratio[i] = (double) val[i] / wt[i];
        }

        // sorting the items in decreasing order of ratio (value per unit weight)
        int[] index = new int[n];
        for (int i = 0; i < n; i++) {
            index[i] = i;
        }
        selectionSort(ratio, index);

        // filling the knapsack using items in decreasing order of ratio (value per unit weight)
        int[] result = new int[n];
        int currentCapacity = 0;
        for (int i = 0; i < n; i++) {
            int itemIndex = index[i];
            if (currentCapacity + wt[itemIndex] <= capacity) {
                result[itemIndex] = 1;
                currentCapacity += wt[itemIndex];
            } else {
                break;
            }
        }
        return result;
    }

    // helper function for sorting the items based on ratio (value per unit weight)
    public static void selectionSort(double[] arr, int[] index) {
        int n = arr.length;
        for (int i = 0; i < n - 1; i++) {
            int maxIndex = i;
            for (int j = i + 1; j < n; j++) {
                if (arr[j] > arr[maxIndex]) {
                    maxIndex = j;
                }
            }
            swap(arr, i, maxIndex);
            swap(index, i, maxIndex);
        }
    }

    // helper function for swapping two items in an array
    public static void swap(double[] arr, int i, int j) {
        double temp = arr[i];
        arr[i] = arr[j];
        arr[j] = temp;
    }

    // helper function for swapping two items in an array
    public static void swap(int[] arr, int i, int j) {
        int temp = arr[i];
        arr[i] = arr[j];
        arr[j] = temp;
    }

    public static void main(String[] args) {
        int[] wt = {10, 20, 30};
        int[] val = {60, 100, 120};
        int capacity = 50;

        int[] result = greedyKnapsack(wt, val, capacity);

        System.out.println("Items in the knapsack:");
        for (int i = 0; i < result.length; i++) {
            if (result[i] == 1) {
                System.out.println("Item " + (i + 1));
            }
        }
    }
}

以上代码实现了一个贪心算法解决背包问题，该算法将物品按照单位重量的价值从大到小排序，然后依次将价值高的物品放入背包中，直到背包装满为止。