第一次作业

group10/595128841/Readme.txt

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+第一次文章地址：http://www.jianshu.com/p/089ac95363d4		如何自己实现一个简单的ArrayList

group10/595128841/src/org/le/ArrayList.java

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+/**
+ * 
+ */
+package org.le;
+
+/**
+ * @author yue
+ * @time 2017年2月19日
+ */
+public class ArrayList<E> implements List<E> {
+
+	private Object[] elementData;
+
+	private int size;
+
+	public ArrayList(int initCapcity){
+		if(initCapcity < 0){
+			throw new IllegalArgumentException("initCapcity 必须大于0");
+		}
+		elementData = new Object[initCapcity];
+	}
+
+	public ArrayList(){
+		elementData = new Object[10];
+	}
+
+	@Override
+	public void add(Object obj) {
+		grow(size + 1);
+		elementData[size++] = obj;
+	}
+
+	@Override
+	public void add(int index, Object obj) {
+		rangeCheckForAdd(index);
+		grow(size + 1);
+		System.arraycopy(elementData, index, elementData, index+1, size - index);
+		elementData[index] = obj;
+		size ++;
+	}
+
+	@Override
+	public void remove(Object obj) {
+		if(obj == null){
+			for (int i = 0; i < size; i++) {
+				if(elementData[i] == null){
+					fastRemove(i);
+				}
+			}
+		}else{
+			for (int i = 0; i < size; i++) {
+				if(obj.equals(elementData[i])){
+					fastRemove(i);
+				}
+			}
+		}
+	}
+
+	@Override
+	public E remove(int index) {
+		rangeCheck(index);
+		int movedNum = size - index - 1;
+		E oldElement = elementData(index);
+		System.arraycopy(elementData, index+1, elementData, index, movedNum);
+		elementData[--size] = null;
+		return oldElement;
+	}
+
+	@Override
+	public E get(int index) {
+		rangeCheck(index);
+		return elementData(index);
+	}
+
+	@Override
+	public E set(int index, E obj) {
+		rangeCheck(index);
+		E oldElement = elementData(index);
+		elementData[index] = obj;
+		return oldElement;
+	}
+
+	@Override
+	public int indexOf(E obj) {
+		if(obj == null){
+			for (int i = 0; i < size; i++) {
+				if(elementData[i] == null){
+					return i;
+				}
+			}
+		}else{
+			for (int i = 0; i < size; i++) {
+				if(obj.equals(elementData[i])){
+					return i;
+				}
+			}
+		}
+		return -1;
+	}
+
+	/**
+	 * 数组扩容
+	 * @param minCapacity
+	 */
+	private void grow(int minCapacity) {
+		if(minCapacity <= elementData.length){
+			return;
+		}
+		int oldCapacity = elementData.length;
+		int newCapacity = minCapacity + (oldCapacity >> 1);
+		if(newCapacity < minCapacity){
+			newCapacity = minCapacity;
+		}
+		if(minCapacity > Integer.MAX_VALUE){
+			newCapacity = Integer.MAX_VALUE;
+		}
+		Object[] newArray = new Object[newCapacity];
+		System.arraycopy(elementData, 0, newArray, 0, newCapacity);
+		elementData = newArray;
+	}
+
+	@SuppressWarnings("unchecked")
+	 private E elementData(int index){
+		return (E) elementData[index];
+	}
+
+	private void fastRemove(int i) {
+		int numMoved = size - i -1;
+		if(numMoved > 0){
+			System.arraycopy(elementData, i+1, elementData, i, numMoved);
+		}
+		elementData[-- size] = null;
+	}
+
+	private void rangeCheck(int index){
+		if(index >= size || index <0)
+			throw new IndexOutOfBoundsException("index:"+index+",size:"+size);
+	}
+
+	private void rangeCheckForAdd(int index){
+		if(index > size || index <0)
+			throw new IndexOutOfBoundsException("index:"+index+",size:"+size);
+	}
+}