如何在Java中搜索保存在我的arraylist中的lastName？

Question

public void searchLastName(String lastName)
{
    int size = list.size();

    for(int i = 0 ; i < size ; i++)
    {
        if(list.get(i).getLastName().equals(lastName))
            System.out.print(lastName+ " is located at " +i);
        else
            System.out.println("Cant find at loc:" +i);

    }
}

is there any problem with this code?? i cant search the lastName.. please help me guys

this is from class Person

public String getLastName() { return lastName; }

Answer 1

What's wrong with your code is that it will print out the "Can't find..." message for all locations that do not match, even if some locations do match. Perhaps that's what you want. However, if you want one location where lastName is found, you can do something like this:

int found = -1;
for (int i = 0; i < size && found == -1; ++i) {
    if (list.get(i).getLastName().equals(lastName)) {
        found = i;
    }
}
if (found >= 0) {
    System.out.print(lastName+ " is located at " + found);
} else {
    System.out.println("Cant find " + lastName);
}

If you want all locations where it is found, you can do this:

List<Integer> found = new ArrayList<Integer>();
for (int i = 0; i < size; ++i) {
    if (list.get(i).getLastName().equals(lastName)) {
        found.add(i);
    }
}
if (found.isEmpty()) {
    System.out.println("Cant find " + lastName);
} else {
    System.out.print(lastName+ " is located at " + found.toString());
}