如何从 ArrayList 中删除条目

Question

I have an ArrayList which is like this;

int a=0;
int b=0;
int c=4;

ArrayList<Integer> al=new ArrayList<Integer>();
al.add(a);
al.add(b);
al.add(c);

I would like to remove all entries which have the value 0 , and become the int c with value 4 to be at index 0 .

How can I do that?

Answer 1

This should work:

for (int i = 0; i < al.size(); i++) {
  if (al.get(i) == 0) {
    al.remove(i);
    i--;
  }
}

Answer 2

Java 8 流方式，虽然可能不适合您（不使用 Java 8，老师没有寻找这种确切的方式等）

al.removeIf(a -> a == 0);

Answer 3

Get an Iterator from the List , iterate it and call Iterator.remove() if the value retrieved is 0 . Something like,

int a = 0, b = 0, c = 4;
List<Integer> al = new ArrayList<>(Arrays.asList(Integer.valueOf(a), b, c));
Iterator<Integer> iter = al.iterator();
while (iter.hasNext()) {
    if (iter.next() == 0) {
        iter.remove();
    }
}
System.out.println(al);

Output is (because 4 is element 0 as requested)

[4]

Answer 4

Arraylist has a method called remove(index i)
It is also has a method called set(index i, element e)
So you would create a loop for the size of the arraylist, check if the value is 0 and if it is call the remove method.
If you want to set the value of index 0 to 4 then use the set method but don't do it in the loop because then it will execute multiple times which is inefficient programming.

Answer 5

I assume this is homework so I won't give the answer. Go https://docs.oracle.com/javase/7/docs/api/java/util/ArrayList.html and look at the Add, Get, and Remove methods. Those methods provide the functionality that you're looking for.

Answer 6

Try this:

for(int i=0;i<al.size();i++){
    if(al.get(i)==0){
         al.remove(i);
         i--;
    }
}

Answer 7

List<Integer> al = new ArrayList<Integer>();
al.add(0);
al.add(0);
al.add(4);
List<Integer> modAl = new ArrayList<Integer>();

Collections.sort(al);

for (int i : al) {
    if (i != 0 ) {
         modAl.add(i);
    }
}
Collections.sort(modAl, Collections.reverseOrder());
al = modAl;
System.out.println(al);

OUTPUT:

[4]