java - 如何检查该对象是否不是最后一个以及如何处理它？

Question

我有一种方法，可以循环遍历一袋几何对象并获取特定属性，并将当前属性与前一个属性(如果有)进行比较，目的是存储最高属性，然后将其分配给另一个几何图形。

我刚刚意识到，在某个时刻我将到达该包的末尾，我需要我的方法来提醒我它已到达包中的最后一个对象。

如何识别当前对象是包中的最后一个对象？

int getLargestUnassignedWard() {
        Bag lsoaGeoms = centroidsLayer.getGeometries();

        System.out.println();
        System.out.println("Getting Largest Unassigned Wards!");

        int highestOSVI = -1;
        MasonGeometry myCopy = null;

        for (Object o : lsoaGeoms) {
            MasonGeometry masonGeometry = (MasonGeometry) o;
            int id = masonGeometry.getIntegerAttribute("ID");
            String lsoaID = masonGeometry.getStringAttribute("LSOA_NAME");
            int tempOSVI = masonGeometry.getIntegerAttribute("L_GL_OSVI_");
            Point highestWard = masonGeometry.geometry.getCentroid();
            System.out.println(lsoaID + " - OSVI rating: " + tempOSVI + ", ID: " + id);
            if (assignedWards.contains(id))
                continue;

            // tempOSVI = the attribute in the "L_GL_OSVI_" column - ints
            if (tempOSVI > highestOSVI) { // if temp is higher than highest
                highestOSVI = tempOSVI; // update highest to temp
                myCopy = masonGeometry; // update myCopy, which is a POLYGON
            }
        }

        if (myCopy == null) {
            System.out.println("ALERT: LSOA Baselayer is null!");
            return -1; // no ID to find if myCopy is null, so just return a fake value
        }

        int id = myCopy.getIntegerAttribute("ID"); // Here, id changes to the highestOSVI
        assignedWards.add(id); // add ID to the "assignedWards" ArrayList
        System.out.println("Highest OSVI Raiting is: " + myCopy.getIntegerAttribute("L_GL_OSVI_") + " for LSOA ID: "
                + id + " (" + myCopy.getStringAttribute("LSOA_NAME") + ")");
        System.out.println("Current list of Largest Unassigned Wards: " + assignedWards); // Prints out: the ID for the highestOSVI
        System.out.println();
        return myCopy.getIntegerAttribute("ROAD_ID"); // return Road_ID for the chosen LSOA to visit
    }

Answer 1

I've just realised that at some point I am going to reach the end of that Bag and I need my method to alert me that it has reached the last object in the bag.

我认为您没有任何理由需要知道这一点才能执行您所说的循环的操作。

但是如果您确实需要知道循环内的情况，则不能使用增强的 for环形;您需要直接使用迭代器:

for (Iterator it = lsoaGeoms.iterator(); it.hasNext(); ) {
    MasonGeometry masonGeometry = (MasonGeometry)it.next();
    boolean isLast = !it.hasNext();
    // ...
}

<小时/>

旁注:我强烈建议使用类型参数而不是原始类型和类型转换。例如，lsoaGeoms将是 Bag<MasonGeometry>等