21.ArrayList内部类迭代器 + java 反射

package com.example.test6;import java.lang.reflect.Constructor;import java.lang.reflect.Field;import java.lang.reflect.InvocationTargetException;import java.lang.reflect.Method;import java.util.Arrays;import java.util.Iterator;/** *  * 使用内部类的方式来实现ArrayList迭代器 *  * 1. ArrayList的构造函数应该是 array = (T[]) new Object[initCapacity] *                       而不是 array = new T[initCapacity[]; *                        * 2. 当删除ArrayList中数组元素的之后，将数组整体往前移动过程中， *    记得将数组size-1位置处引用值为空，帮助GC尽早释放资源 *  */class ArrayList<T> implements Iterable<T>{		PRivate T[] array;	private int size;	public ArrayList() {			this(10);	}		public ArrayList(int initCapacity){		array = (T[]) new Object[initCapacity];		size = 0;	}		public void add(T value){		if (size >= array.length){			array = Arrays.copyOf(array, array.length * 2);		}		array[size++] = value;	}		public void del(T value){		for (int i = 0; i < size; i++){			if (array[i].equals(value)){				System.arraycopy(array, i+1, array, i, size-i-1);				size--;				array[size] = null;			}		}	}		public T get(int index){		if (index < 0 || index >= size){			throw new IndexOutOfBoundsException();		}				return array[index];	}		public String toString(){		StringBuilder s = new StringBuilder();		s.append("[");				for (int i = 0; i < size; i++){			s.append(array[i] + " ");		}		s.append("]");				return s.toString();	}	@Override	public Iterator<T> iterator() {		// TODO Auto-generated method stub		return new MyIterator();	}		class MyIterator implements Iterator<T>{				private int index;				public MyIterator(){			index = 0;		}		@Override		public boolean hasNext() {			// TODO Auto-generated method stub			return index < ArrayList.this.size;		}		@Override		public T next() {			// TODO Auto-generated method stub			return ArrayList.this.array[index++];		}		/**		 * 		 * 删除当前index下标处的元素		 */		@Override		public void remove() {			// TODO Auto-generated method stub			if (index >= size){				return;			}						System.arraycopy(array, index+1, array, index, size-index-1);			size--;			array[size] = null;		}	}	}public class TestDemo {	public static void main(String[] args) {		// TODO Auto-generated method stub		ArrayList<Integer> list = new ArrayList<Integer>();				for (int i = 0; i < 15; i++){			list.add(i);		}				System.out.println(list);				Iterator<Integer> it = list.iterator();		while (it.hasNext()){			it.remove();		}				System.out.println(list);				try {			Class<?> c = Class.forName("com.example.test6.ArrayList");						Constructor<?>[] cons = c.getConstructors();			for (Constructor<?> con : cons){				System.out.println(con);			}						//通过反射调用构造函数生成类对象						//调用默认构造函数生成类对象			ArrayList<Integer> list1 = (ArrayList)c.newInstance();			for (int i = 0; i < 10; i++){				list1.add(i);			}			System.out.println(list1);						//通过调用带参数的构造函数生成类对象			Constructor<?> con = c.getConstructor(int.class);			ArrayList<Integer> list2 = (ArrayList<Integer>) con.newInstance(10);			for (int i = 0; i < 10; i++){				list2.add(i);			}			System.out.println(list2);						//////////////////////////////////////////////						//通过反射调用类的成员变量			Field[] fields = c.getDeclaredFields();			for (Field field : fields){				System.out.println(field);			}						Field field = c.getDeclaredField("size");			field.setaccessible(true);			field.setInt(list2, 5);			System.out.println(list2);						///////////////////////////////////////////////						//通过反射调用类的成员方法						Method[] methods = c.getDeclaredMethods();			for (Method method : methods){				System.out.println(method);			}						Method method = c.getMethod("get", int.class);			Integer value = (Integer) method.invoke(list2, 3);			System.out.println(value);					} catch (ClassNotFoundException e) {			// TODO Auto-generated catch block			e.printStackTrace();		} catch (InstantiationException e) {			// TODO Auto-generated catch block			e.printStackTrace();		} catch (IllegalAccessException e) {			// TODO Auto-generated catch block			e.printStackTrace();		} catch (NoSuchMethodException e) {			// TODO Auto-generated catch block			e.printStackTrace();		} catch (SecurityException e) {			// TODO Auto-generated catch block			e.printStackTrace();		} catch (IllegalArgumentException e) {			// TODO Auto-generated catch block			e.printStackTrace();		} catch (InvocationTargetException e) {			// TODO Auto-generated catch block			e.printStackTrace();		} catch (NoSuchFieldException e) {			// TODO Auto-generated catch block			e.printStackTrace();		}	}}