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[英]How can I remove an ArrayList from an ArrayList of ArrayLists?
[英]How can I remove an Item from an ArrayList given the itemNum?
我想刪除用戶將輸入的ItemNo項目。 如何檢查是否存在此項目的項目? 然后我怎么把它刪除? 以下是我到目前為止,我需要添加CompareTo()
方法嗎?
物品類別:
public class Item {
public int itemNo;
public String itemName;
public double itemPrice;
public int itemQuantity;
Item(int number, String name, double price, int quantity)
{
itemNo=number;
itemName=name;
itemPrice=price;
itemQuantity=quantity;
}
刪除方法:
public T remove(int givenPosition) {
T result = null;
if ((givenPosition >= 1) && (givenPosition <= numberOfEntries)) {
assert !isEmpty();
result = list[givenPosition - 1];
if (givenPosition < numberOfEntries)
removeGap(givenPosition);
numberOfEntries--;
} // end if
return result;
} // end remove
包含方法:
public boolean contains(T anEntry) {
boolean found = false;
for (int index = 0; !found && (index < numberOfEntries); index++) {
if (anEntry.equals(list[index]))
found = true;
}//end for
return found;
} // end contains
等於方法:
public boolean equals(Object object){
Item item = (Item) object;
if(itemNo == item.itemNo)
return true;
return false;
}
好吧,你正試圖分離邏輯,但我會給你你的問題的代碼片段。
Item item = new Item(10 , "Item1", 50 , 100);
Item item2 = new Item(20 , "Item2", 50 , 100);
Item item3 = new Item(30 , "Item3", 50 , 100);
List<Item> itemList = new ArrayList<Item>();
itemList.add(item1);
itemList.add(item2);
itemList.add(item3);
public void removeItem(int itemNo){
Iterator<Item> it = itemList.iterator();
while(it.hasNext){
if(item.next().itemNo == itemNo){
it.remove;
break;
}
}
}
由於Java8任何Collection(如List)都有removeIf(Predicate<? super E> filter)
方法,它可以刪除項匹配過濾器。 所以你的代碼看起來像
list.removeIf(item -> item.getItemNo() == x );//where x is value you want to remove
private void removeObjectWithNumber(int number) {
for (int i = 0; i < list.size(); i++) {
Item item = list.get(i);
if (item.getItemNo() == number) {
list.remove(i);
return;
}
}
}
使用ArrayList:
添加:
ArrayList<Item> mList = new ArrayList<Item>();
mList.add(new Item(101, "Television", 20000, 4));
mList.add(new Item(102, "Mobile", 6000, 4));
去掉 :
mList.remove(i /* index */);
包含:
// override equals method in class
@Override
public boolean equals(Object v) {
boolean retVal = false;
if (v instanceof A){
A ptr = (A) v;
retVal = ptr.itemNo.longValue() == this.itemNo;
// if you want to check more then you can do
// retVal = ptr.itemName.toString().equals(this.itemName.toString());
// further same for itemPrice, itemQuantity
}
return retVal;
}
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