(Java) 从数组列表中删除所有出现的值

Question

For my computer science class I need to make a program using IntegerList.java that completes the following:

1. Add this capability to the IntegerList class. You will need to add an increaseSize method plus instance variables to hold the current number of integers in the list and the current size of the array. Since you do not have any way to add elements to the list, you won't need to call increaseSize yet.

2. Add a method void addElement(int newVal) to the IntegerList class that adds an element to the list. At the beginning of addElement, check to see if the array is full. If so, call increaseSize before you do anything else.

3. Add a method void removeFirst(int newVal) to the IntegerList class that removes the first occurrence of a value from the list. If the value does not appear in the list, it should do nothing (but it's not an error). Removing an item should not change the size of the array, but note that the array values do need to remain contiguous, so when you remove a value you will have to shift everything after it down to fill up its space. Also remember to decrement the variable that keeps track of the number of elements.

4. Add a method removeAll(int newVal) to the IntegerList class that removes all occurrences of a value from the list. If the value does not appear in the list, it should do nothing (but it's not an error). Add an option to the menu in IntegerListTest to test your new method.

I have finished everything except number 4 , which I am stuck on. I'm not sure how to remove all occurrences of a value from the list. Here is my code for the rest of the program.

Integer List

public class IntegerList
{
    private int count;
    private double totalInt;
    int[] list; //values in the list

    //-------------------------------------------------------
    //create a list of the given size
    //-------------------------------------------------------
    public IntegerList(int size)
    {
        list = new int[size];
        count = 0;
    }

    //-------------------------------------------------------
    //fill array with integers between 1 and 100, inclusive
    //-------------------------------------------------------
    public void randomize()
    {
        for (int i = 0; i < list.length; i++)
            list[i] = (int)(Math.random() * 100) + 1;
    }

    //-------------------------------------------------------
    //print array elements with indices
    //-------------------------------------------------------
    public void print()
    {
        for (int i = 0; i < count; i++)
            System.out.println(i + ":\t" + list[i]);
    }

    public void increaseSize()//int size???
    {
        int[] temp = new int[list.length * 2];

        for (int i = 0; i < list.length; i++)
            temp[i] = list[i];

        list = temp;
    }

    public void addElement(int newVal)
    {
        if (count == list.length)
           increaseSize();

        list[count] = newVal;
        count++;
    }

    public void removeFirst(int newVal2)
    {
        int index = -1;
        for (int i = 0; i < count; i++)
        {
            index = i;

            if (index != -1) {
               // this code handles after found case
               if (i == count-1)
               {
                 // zero-out last element
                 list[i] = 0;
                 count--;
               }
               else
               {
                 // shift value
                 list[i] = list[i+1];
               }
            }
        }
    }

    public void removeAll(int newVal)
    {
       //This is the part I'm stuck on
    }
}

IntegerListTest

import java.util.Scanner;
public class IntegerListTest
{
    static IntegerList list = new IntegerList(10);
    static Scanner scan = new Scanner(System.in);

    //-------------------------------------------------------
    // Create a list, then repeatedly print the menu and do what the
    // user asks until they quit
    //-------------------------------------------------------
    public static void main(String[] args)
    {
        printMenu();
        int choice = scan.nextInt();
        while (choice != 0)
        {
            dispatch(choice);
            printMenu();
            choice = scan.nextInt();
        }
    }

    //--------------------------------------
    // Do what the menu item calls for
    //--------------------------------------
    public static void dispatch(int choice)
    {
        int loc;
        switch(choice)
        {
            case 0:
                System.out.println("Bye!");
                break;

            case 1:
            System.out.println("How big should the list be?");
            int size = scan.nextInt();
            list = new IntegerList(size);
            list.randomize();
            break;

            case 2:
            list.print();
            break;

            case 3:
            System.out.println("What number would you like to add?");
            int newVal = scan.nextInt();
            list.addElement(newVal);
            break;

            case 4:
            System.out.println("What number do you want to remove? "
                + "(Removes first occurance.)");
            int newVal2 = scan.nextInt();
            list.removeFirst(newVal2);

            case 5: //This is the part I am stuck on
            System.out.println("What number do you wish to remove?"
                + "(Removes all occurances.)");


            default:
            System.out.println("Sorry, invalid choice");
        }
    }

    //----------------------------
    // Print the user's choices
    //----------------------------
    public static void printMenu()
    {
        System.out.println("\n Menu ");
        System.out.println(" ====");
        System.out.println("0: Quit");
        System.out.println("1: Create a new list (** do this first!! **)");
        System.out.println("2: Print the list");
        System.out.println("3: Add element to the list");
        System.out.println("4: Remove a value from the list");
        System.out.println("5: Remove all occurrences of a value from the list");
        System.out.print("\nEnter your choice: ");
    }
}

Answer 1

I would use the code you have already written with some slight modifications. I almost never write a method with the return type of void. I want to have the option to know if my method was successful or not. Returning a boolean for your removeFirst() can come in handy when debugging or testing (JUnit). Just because the method now returns a boolean doesn't mean you have to use it, you can still call the method in the same way you are right now in your code with

list.removeFirst(newVal2);

You only need to modify your method removeFirst() to return a boolean instead of void.

boolean removeFirst(int valToDelete) - 
    //True - found the value you were looking for and successfully removed it from the list
    //False - the value to delete doesn't exist in your list

Then all there is left to do is use that method in a while loop like so

boolean removeAll(int val)
{
    boolean retVal = false;
    do{
        retVal = removeFirst(val);
    }while(retVal);

    return retVal;
}

This simple modification to removeFirst() allows re-usability in your class

As an example, Java's own ArrayList method for remove() returns a boolean