复习(数据结构：java)：线性表（数组）：泛型的写法

• 将 $ArrayIntList$ 转换为 $ArrayList<E>$

//原始函数
public ArrayIntList(int capacity){
    if(capacity < 0)
        throw new IllegalArgumentException("cpapcity: "+capacity);
    elementData = new int[capacity];
    size=0;
}
//直接泛化，会错误
// 不可以创建泛型的数组
//可以创建Object[]数组

public ArrayIntList(E capacity){
    if(capacity < 0)
        throw new IllegalArgumentException("cpapcity: "+capacity);
    elementData = new E[capacity];
    size=0;
}

//修改后的泛型；
//可以消除注释的方法
//@suppressWarining("unchecked")
public ArrayIntList(E capacity){
    if(capacity < 0)
        throw new IllegalArgumentException("cpapcity: "+capacity);
    elementData = （E()）new object[capacity];
    size=0;
}

• “==”和 equals的区别
  

//原函数
public int indexof(E value){
    for(int i=0;i<size;i++){
        if(elementData[i]==value)
            return i;
    }

    return -1;
}

//修改

public int indexof(E value){
    for(int i=0;i<size;i++){
        if(elementData[i]。equals(value))
            return i;
    }

    return -1;
}

• 内部类
• 在类的内部声明一个类，内部的类的对象，可以访问外部类的方法和字段
• $ArryaListIterator<E> 继承自 Iterator<E>$

private class ArrayListIterator implements Iterator<E> {
        private int position;           // current position within the list
        private boolean removeOK;       // whether it's okay to remove now

        // post: constructs an iterator for the given list
        public ArrayListIterator() {
            position = 0;
            removeOK = false;
        }

        // post: returns true if there are more elements left, false otherwise
        public boolean hasNext() {
            return position < size();
        }

        // pre : hasNext() (throws NoSuchElementException if not)
        // post: returns the next element in the iteration
        public E next() {
            if (!hasNext()) {
                throw new NoSuchElementException();
            }
            E result = elementData[position];
            position++;
            removeOK = true;
            return result;
        }

        // pre : next() has been called without a call on remove (throws
        //       IllegalStateException if not)
        // post: removes the last element returned by the iterator
        public void remove() {
            if (!removeOK) {
                throw new IllegalStateException();
            }
            ArrayList.this.remove(position - 1);
            position--;
            removeOK = false;
        }
    }