ArrayList提交

ThinkPad · ThinkPad · commit 317f47ae9dee · 2017-02-26T15:56:56.000+08:00
diff --git a/group08/121027265/0226/src/com/my/list/ArrayList.java b/group08/121027265/0226/src/com/my/list/ArrayList.java
@@ -1,5 +1,131 @@
 package com.my.list;
 
+/**
+ * 实现ArrayList
+ *
+ */
 public class ArrayList {
+	//初始化容量
+	private static final int INIT = 5;
+	//增长因子
+	private static final double GROWTH = 0.5;
+	
+	//初始化数组
+	Object[] baseArr = new Object[INIT];
+	//当前下标
+	int currentIndex = 0;
+	//最大下标
+	int maxIndex = INIT-1;
+	
+	/**
+	 * 添加元素
+	 * @param obj
+	 * @return
+	 */
+	public Object add(Object obj){
+		if(judgeCapacity()){
+			baseArr = arrayDilatation(baseArr, GROWTH);
+			maxIndex = baseArr.length-1;
+		}
+		baseArr[currentIndex] = obj;
+		++currentIndex;
+		return obj;
+	}
+	
+	/**
+	 * 指定下标添加元素
+	 * @param index
+	 * @param obj
+	 * @return
+	 */
+	public Object add(int index , Object obj){
+		if (index < 0 || index > currentIndex) {
+			throw new IndexOutOfBoundsException();
+		}
+		Object[] dest = new Object[currentIndex+1];
+		System.arraycopy(baseArr, 0, dest, 0, index);
+		dest[index] = obj;
+		System.arraycopy(baseArr, index, dest, index+1, currentIndex-index);
+		++currentIndex;
+		baseArr = dest;
+		return obj;
+	}
+	
+	/**
+	 * 指定下标删除元素 
+	 * @param index
+	 * @return
+	 */
+	public Object remove(int index){
+		if (index < 0 || index >= currentIndex) {
+			throw new IndexOutOfBoundsException();
+		}
+		Object object = baseArr[index];
+		Object[] dest = new Object[currentIndex];
+		System.arraycopy(baseArr, 0, dest, 0, index);
+		System.arraycopy(baseArr, index+1, dest, index, currentIndex-index-1);
+		--currentIndex;
+		baseArr = dest;
+		return object;
+	}
+	
+	/**
+	 * 根据下标获取元素
+	 * @param index
+	 * @return
+	 */
+	public Object get(int index){
+		
+		return baseArr[index];
+	}
+	
+	/**
+	 * 获取集合大小
+	 * @return
+	 */
+	public int size(){
+		return currentIndex;
+	}
+	
+	/**
+	 * 判断容量是否需要增加
+	 * @return
+	 */
+	public boolean judgeCapacity(){
+		if(currentIndex > maxIndex){
+			return true;
+		}
+		return false;
+	}
+	
+	/**
+	 * 数组扩容
+	 * @param objArr
+	 * @param groth
+	 * @return
+	 */
+	public static Object[] arrayDilatation(Object[] objArr , double groth){
+		   int length = objArr.length;
+		   int newLength = (int) (length * groth + length);
+		   Object[] baseArr = new Object[newLength];
+		   System.arraycopy(objArr, 0, baseArr, 0, length);
+		   return baseArr;
+	}
+	
 
 }
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
diff --git a/group08/121027265/0226/src/com/my/list/Test.java b/group08/121027265/0226/src/com/my/list/Test.java
@@ -0,0 +1,36 @@
+package com.my.list;
+
+public class Test {
+
+	public static void main(String[] args) {
+		testArrayList();
+		
+
+	}
+	
+	/**
+	 * list 测试
+	 */
+	public static void testArrayList(){
+		ArrayList list = new ArrayList();
+		list.add("123");
+		list.add("123");
+		list.add("123");
+		list.add("123");
+		list.add("123");
+		list.add("123");
+		
+		list.add(1, 111);
+		
+		list.remove(1);
+		
+		System.out.println(list.baseArr.length);
+		System.out.println(list.size());
+		
+		for (int i = 0; i < list.size(); i++) {
+			Object object = list.get(i);
+			System.out.println(object);
+		}
+	}
+
+}
