从Java中的链接列表中删除所有错误的元素

Question

I have a linked list of fish data shown here

 //create linked list of fish data called fl
    LinkedList<FishData> fl = new LinkedList<FishData>();
    //Here are a few data items
    fl.add(new FishData("American Eel ", 9, "Summer/Spring ", 25 , false));
    fl.add(new FishData("Hammerhead Shark ", 0, "All Year ", 36, false));
    fl.add(new FishData("Horseshoe Crab ", 7, "All Year except May ", 60, false));
    fl.add(new FishData("Haddock ", 18, "All Year ", 0, true));
    fl.add(new FishData("Tautog ", 16, "late Spring to end of year ", 3, true));

I have to use an iterator to remove all of the false elements from this list and print it again. I think i understand how it works logically, if my data items were only comprised of booleans i think what i did would work, however i dont know how to look at just the boolean field of the element and remove it if its false. this is what i tried and got a class cast exception, i know what that means i just dont know how to fix it.

Iterator itr = fl.iterator();
    while (itr.hasNext()) {
        boolean w = (boolean) itr.next();
        if (w = false)
            itr.remove();
    }

UPDATE:

so i edited the code and i now have this

 Iterator<FishData> itr = fl.iterator();
    while (itr.hasNext()) {
        FishData b = (FishData) itr.next();
        if (!b.w) {
            itr.remove();
        }
    }
    for (FishData element : fl) {
        System.out.println(element);
    }
}

previously i used that for loop to print the whole list but when i use it now, nothing prints

Answer 1

itr.next() will return the next element in your LinkedList , which will be a FishData object. You cannot cast this to a boolean variable. Instead you want to access the boolean variable of the fishData object. So assuming that your FishData class has a someCondition boolean variable you can do:

while (itr.hasNext()) {
    boolean w = itr.next().someCondition;
    if (w = false)
        itr.remove();
}

Or if it is a private variable and you have a getter method:

while (itr.hasNext()) {
    boolean w = itr.next().isSomeCondition();
    if (w = false)
        itr.remove();
}

Also the line if(w = false) is incorrect. = is the assignment operator. You either need to do if(w == false) or if(!w) . Or you could simplify this to:

while (itr.hasNext()) {
    if (!itr.next().isSomeCondition())
        itr.remove();
}

Additionally you need to create a more specific Iterator :

Iterator<FishData> itr = fl.iterator();