我正在做这个狂欢编程，它想要将某些东西实现到 MyLinkedList 中 我想我已经明白了它的要点，但我仍然无法弄清楚，狂欢希望我使用这个：https://liveexample.pearsoncmg.com/test/Exercise24_01_13e.txt
我试图实现的方法是 addAll、removeAll、retainAll、containsAll、toArray() 和 toArray(T[])
import java.util.*;
public class Exercise24_01 {
public static void main(String[] args) {
new Exercise24_01();
}
public Exercise24_01() {
Scanner input = new Scanner(System.in);
String[] name1 = new String[5];
String[] name2 = new String[5];
String[] name3 = new String[2];
System.out.print("Enter five strings for array name1 separated by space: ");
for (int i = 0; i < 5; i++) {
name1[i] = input.next();
}
System.out.print("Enter five strings for array name2 separated by space: ");
for (int i = 0; i < 5; i++) {
name2[i] = input.next();
}
System.out.print("Enter two strings for array name3 separated by space: ");
for (int i = 0; i < 2; i++) {
name3[i] = input.next();
}
MyList<String> list1 = new MyArrayList<>(name1);
MyList<String> list2 = new MyArrayList<>(name2);
System.out.println("list1: " + list1);
System.out.println("list2: " + list2);
list1.addAll(list2);
System.out.println("After addAll: list1 is " + list1 + "\n");
list1 = new MyArrayList<>(name1);
list2 = new MyArrayList<>(name2);
System.out.println("list1: " + list1);
System.out.println("list2: " + list2);
list1.removeAll(list2);
System.out.println("After removeAll: list1 is " + list1 + "\n");
list1 = new MyArrayList<>(name1);
list2 = new MyArrayList<>(name2);
System.out.println("list1: " + list1);
System.out.println("list2: " + list2);
list1.retainAll(list2);
System.out.println("After retainAll: list1 is " + list1 + "\n");
list1 = new MyArrayList<>(name1);
list2 = new MyArrayList<>(name2);
System.out.println("list1: " + list1);
System.out.println("list2: " + list2);
list1.retainAll(list2);
System.out.println("list1 contains all list2? " + list1.containsAll(list2) + "\n");
list1 = new MyArrayList<>(name1);
list2 = new MyArrayList<>(name3);
System.out.println("list1: " + list1);
System.out.println("list2: " + list2);
System.out.println("list1 contains all list2? " + list1.containsAll(list2) + "\n");
Object[] name4 = list1.toArray();
System.out.print("name4: ");
for (Object e: name4) {
System.out.print(e + " ");
}
String[] name5 = new String[list1.size()];
String[] name6 = list1.toArray(name5);
System.out.print("\nname6: ");
for (Object e: name6) {
System.out.print(e + " ");
}
}
}
class MyArrayList<E> implements MyList<E> {
public static final int INITIAL_CAPACITY = 16;
private E[] data = (E[])new Object[INITIAL_CAPACITY];
private int size = 0; // Number of elements in the list
/** Create an empty list */
public MyArrayList() {
}
/** Create a list from an array of objects */
public MyArrayList(E[] objects) {
for (int i = 0; i < objects.length; i++)
add(objects[i]); // Warning: don't use super(objects)!
}
@Override /** Add a new element at the specified index */
public void add(int index, E e) {
ensureCapacity();
// Move the elements to the right after the specified index
for (int i = size - 1; i >= index; i--)
data[i + 1] = data[i];
// Insert new element to data[index]
data[index] = e;
// Increase size by 1
size++;
}
/** Create a new larger array, double the current size + 1 */
private void ensureCapacity() {
if (size >= data.length) {
E[] newData = (E[])(new Object[size * 2 + 1]);
System.arraycopy(data, 0, newData, 0, size);
data = newData;
}
}
@Override /** Clear the list */
public void clear() {
data = (E[])new Object[INITIAL_CAPACITY];
size = 0;
}
@Override /** Return true if this list contains the element */
public boolean contains(Object e) {
for (int i = 0; i < size; i++)
if (e.equals(data[i])) return true;
return false;
}
@Override /** Return the element at the specified index */
public E get(int index) {
checkIndex(index);
return data[index];
}
private void checkIndex(int index) {
if (index < 0 || index >= size)
throw new IndexOutOfBoundsException
("Index: " + index + ", Size: " + size);
}
@Override /** Return the index of the first matching element
* in this list. Return -1 if no match. */
public int indexOf(Object e) {
for (int i = 0; i < size; i++)
if (e.equals(data[i])) return i;
return -1;
}
@Override /** Return the index of the last matching element
* in this list. Return -1 if no match. */
public int lastIndexOf(E e) {
for (int i = size - 1; i >= 0; i--)
if (e.equals(data[i])) return i;
return -1;
}
@Override /** Remove the element at the specified position
* in this list. Shift any subsequent elements to the left.
* Return the element that was removed from the list. */
public E remove(int index) {
checkIndex(index);
E e = data[index];
// Shift data to the left
for (int j = index; j < size - 1; j++)
data[j] = data[j + 1];
data[size - 1] = null; // This element is now null
// Decrement size
size--;
return e;
}
@Override /** Replace the element at the specified position
* in this list with the specified element. */
public E set(int index, E e) {
checkIndex(index);
E old = data[index];
data[index] = e;
return old;
}
@Override
public String toString() {
StringBuilder result = new StringBuilder("[");
for (int i = 0; i < size; i++) {
result.append(data[i]);
if (i < size - 1) result.append(", ");
}
return result.toString() + "]";
}
/** Trims the capacity to current size */
public void trimToSize() {
if (size != data.length) {
E[] newData = (E[])(new Object[size]);
System.arraycopy(data, 0, newData, 0, size);
data = newData;
} // If size == capacity, no need to trim
}
@Override /** Override iterator() defined in Iterable */
public java.util.Iterator<E> iterator() {
return new ArrayListIterator();
}
private class ArrayListIterator
implements java.util.Iterator<E> {
private int current = 0; // Current index
@Override
public boolean hasNext() {
return (current < size);
}
@Override
public E next() {
return data[current++];
}
@Override
public void remove() {
if (current == 0) // next() has not been called yet
throw new IllegalStateException();
MyArrayList.this.remove(--current);
}
}
@Override /** Return the number of elements in this list */
public int size() {
return size;
}
}
interface MyList<E> extends java.util.Collection<E> {
// WRITE YOUR CODE HERE
/** Add a new element at the specified index in this list */
public void add(int index, E e);
/** Return the element from this list at the specified index */
public E get(int index);
/** Return the index of the first matching element in this list.
* Return -1 if no match. */
public int indexOf(Object e);
/** Return the index of the last matching element in this list
* Return -1 if no match. */
public int lastIndexOf(E e);
/** Remove the element at the specified position in this list
* Shift any subsequent elements to the left.
* Return the element that was removed from the list. */
public E remove(int index);
/** Replace the element at the specified position in this list
* with the specified element and returns the new set. */
public E set(int index, E e);
@Override /** Add a new element at the end of this list */
public default boolean add(E e) {
add(size(), e);
return true;
}
@Override /** Return true if this list contains no elements */
public default boolean isEmpty() {
return size() == 0;
}
@Override /** Remove the first occurrence of the element e
* from this list. Shift any subsequent elements to the left.
* Return true if the element is removed. */
public default boolean remove(Object e) {
if (indexOf(e) >= 0) {
remove(indexOf(e));
return true;
}
else
return false;
}
@Override
public default boolean containsAll(Collection<?> c) {
// Left as an exercise
boolean containE;
for (E e: c) {
if (contains(c)) {
containE = true;
} else {
containE = false;
}
}
if (containE != true) {
return false;
}
return true;
}
@Override
public default boolean addAll(Collection<? extends E> c) {
// Left as an exercise
boolean addE;
for (E e : c) {
if (add(e)) {
addE = true;
} else {
addE = false;
}
}
if (addE != true) {
return false;
}
return true;
}
@Override
public default boolean removeAll(Collection<?> c) {
// Left as an exercise
boolean removeE;
for (E e : c) {
if (remove(e)) {
removeE = true;
} else {
removeE = false;
}
}
if (removeE != true) {
return false;
}
return true;
}
@Override
public default boolean retainAll(Collection<?> c) {
// Left as an exercise
boolean retainE;
for (E e : c) {
if (retain(e)) {
retainE = true;
} else {
retainE = false;
}
}
if (retainE != true) {
return false;
}
return true;
}
@Override
public default Object[] toArray() {
// Left as an exercise
Object[] array = new Object[]();
for (int i = 0; i < array.length(); i++) {
Object[i] = array[i];
}
return null;
}
@Override
public default <T> T[] toArray(T[] array) {
// Left as an exercise
for (E element : array) {
System.out.println(element);
}
System.out.println();
return null;
}
}
但出来的只有这个：
----jGRASP exec: javac -g --module-path C:\Users\rmeri\Downloads\openjfx-19_windows-x64_bin-sdk\javafx-sdk-19\lib --add-modules=javafx.controls -Xlint:unchecked Exercise24_01.java
Exercise24_01.java:361: error: array dimension missing
Object[] array = new Object[]();
^
1 error
----jGRASP wedge2: exit code for process is 1.
----jGRASP: operation complete.
如果有人可以帮助我，我将非常感激，但默认方法无法更改。
正确的数组声明看起来更像这样：
Object[] array = new Object[]{};ArrayList<>() array = new ArrayList<>();顺便说一句，尝试查看错误消息并尝试自己解码！学习如何阅读错误消息对于解决问题非常重要！ 希望这有帮助！