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MyArrayList.java
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164 lines (120 loc) · 3.29 KB
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import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.Objects;
import java.util.function.Consumer;
/**
* Created by liufengkai on 16/7/8.
*/
public class MyArrayList<AnyType> implements Iterator<AnyType> {
private static final int DDEFAULT_CAPACITY = 10;
private int theSize;
private AnyType[] theItems;
public MyArrayList() {
clear();
}
public void clear() {
theSize = 0;
ensureCapacity(DDEFAULT_CAPACITY);
}
public int size() {
return theSize;
}
public boolean isEmpty() {
return size() == 0;
}
public void trimToSize() {
ensureCapacity(size());
}
public AnyType get(int idx) {
if (idx < 0 || idx >= size()) {
throw new ArrayIndexOutOfBoundsException();
}
return theItems[idx];
}
public AnyType set(int idx, AnyType newVal) {
if (idx < 0 || idx >= size()) {
throw new ArrayIndexOutOfBoundsException();
}
AnyType old = theItems[idx];
theItems[idx] = newVal;
return old;
}
public void ensureCapacity(int newCapacity) {
if (newCapacity < theSize)
return;
AnyType[] old = theItems;
theItems = (AnyType[]) new Object[newCapacity];
for (int i = 0; i < size(); i++) {
theItems[i] = old[i];
}
}
public boolean add(AnyType x) {
add(size(), x);
return true;
}
public void add(int index, AnyType x) {
if (theItems.length == size()) {
ensureCapacity(size() * 2 + 1);
}
for (int i = theSize; i > index; i--) {
theItems[i] = theItems[i - 1];
}
theItems[index] = x;
theSize++;
}
public AnyType remove(int index) {
AnyType removeItem = theItems[index];
for (int i = index; i < size() - 1; i++) {
theItems[i] = theItems[i + 1];
}
theSize--;
return removeItem;
}
public Iterator<AnyType> iterator() {
return new ArrayListIterator();
}
private class ArrayListIterator implements Iterator<AnyType> {
private int current = 0;
@Override
public boolean hasNext() {
return current < size();
}
@Override
public AnyType next() {
if (!hasNext())
throw new NoSuchElementException();
return theItems[current++];
}
@Override
public void remove() {
MyArrayList.this.remove(--current);
}
}
@Override
public boolean hasNext() {
return false;
}
@Override
public AnyType next() {
return null;
}
@Override
public void remove() {
}
@Override
public void forEachRemaining(Consumer<? super AnyType> action) {
Objects.requireNonNull(action);
while (hasNext())
action.accept(next());
}
public static void main(String[] args) {
MyArrayList<String> list = new MyArrayList<>();
for (int i = 0; i < 10; i++) {
list.add("i = " + i);
}
Iterator<String> iterator = list.iterator();
while (iterator.hasNext()) {
System.out.println(iterator.next());
}
}
}