Question

我对number array中Java对象中class删除所有元素有疑问，不建议使用ArrayList ，方法但只是因为它们在数组中的位置

而只是因为它没有消除一些元素而使一些元素被修改

public class Pack { static int nextNumber = 0; int number; String name; public Pack(String name) { this.number = ++nextNumber; this.name = name; } @Override public String toString() { return "Pack ID:" + number + " - Name: " + name; } } 打包

class

class Container { static int nextNumber = 0; int number; int qtPack; Pack[] packs; public Container() { this.number = ++nextNumber; this.qtPack = 0; this.packs = new Pack[10]; } public boolean addPack(Pack pack) { packs[qtPack] = pack; qtPack++; return true; } public Pack removePack(int numberPack) { int idx; Pack removePack = null; idx = indexOfPackByID(numberPack); if (idx != -1) { removePack = packs[idx]; if (removePack != null) { for (int i = idx; i < qtPack - 1; i++) { packs[i] = packs[i + 1]; } qtPack--; } } return removePack; } private int indexOfPackByID(int numberPack) { for (int i = 0; i < qtPack; i++) { if ((packs[i] != null) && (packs[i].number == numberPack)) { return i; } } return -1; } } 容器

class

public class Main { public static void main(String[] args) { Pack[] packs = new Pack[5]; packs[0] = new Pack("A"); packs[1] = new Pack("B"); packs[2] = new Pack("C"); packs[3] = new Pack("D"); packs[4] = new Pack("E"); Container container = new Container(); for (int i = 0; i < packs.length; i++) { container.addPack(packs[i]); } System.out.println("--- PACK IN CONTAINER ---"); for (int i = 0; i < container.qtPack; i++) { System.out.println(container.packs[i].toString()); } System.out.println("\n--- REMOVE PACK ---"); for (int i = 0; i < container.qtPack; i++) { Pack pack = container.removePack(container.packs[i].number); System.out.println("Remove " + pack.name+" - ID: "+pack.number); } } } 主要

Main

--- PACK IN CONTAINER --- Pack ID:1 - Name: A Pack ID:2 - Name: B Pack ID:3 - Name: C Pack ID:4 - Name: D Pack ID:5 - Name: E --- REMOVE PACK --- Remove A - ID: 1 Remove C - ID: 3 Remove E - ID: 5

的输出

class FooData(object):
    def __init__(self):
        ...
        try:
            self.my_cnf = os.environ['HOME'] + '/.my.cnf'
            self.my_cxn = mysql.connector.connect(option_files=self.my_cnf)
            self.cursor = self.my_cxn.cursor(dictionary=True)
        except mysql.connector.Error as err:
            if err.errno == 2003:
                self.my_cnf = None
                self.my_cxn = None
                self.cursor = None

任何建议？

Answer 1

仔细查看Container.removePack()

for (int i = idx; i < qtPack - 1; i++) {
    packs[i] = packs[i + 1];
}

每次调用removePack()时，container都会将packs[]的某些元素引用到“下一个”Pack。因此removePack()之后pack []不一样。

Answer 2

你可以从最后删除它们......

    for (int i = container.qtPack-1; i >= 0; i--) {
        Pack pack = container.removePack(container.packs[i].number);
        System.out.println("Remove " + pack.name+" - ID: "+pack.number);
    }

...或总是删除第一个元素：

    int count = container.qtPack;
    for (int i = 0; i < count; i++) {
        Pack pack = container.removePack(container.packs[0].number);
        System.out.println("Remove " + pack.name+" - ID: "+pack.number);
    }

这是因为通过更改数组，您每次迭代都会更改条件（此处为container.packs和container.qtPack）。请记住，每次迭代都会计算循环条件i < container.qtPack。

从Java中删除数组中的所有元素

2 个答案: