ArrayList(The ikook implementation)

ikook-wang · ikook-wang · commit 794fea5d2ca5 · 2017-02-23T17:50:30.000+08:00
diff --git a/group18/935542673/Coding/junit/com/ikook/basic_data_structure/MyArrayListTest.java b/group18/935542673/Coding/junit/com/ikook/basic_data_structure/MyArrayListTest.java
@@ -0,0 +1,75 @@
+package com.ikook.basic_data_structure;
+
+import static org.junit.Assert.*;
+
+import java.util.Date;
+
+import org.junit.Before;
+import org.junit.Test;
+
+/**
+ * 此单元测试只测试了正常情况，一些异常情况没有测试。
+ * @author ikook
+ */
+public class MyArrayListTest {
+	
+	private MyArrayList list;
+	
+	@Before
+	public void setUp() {
+		list = new MyArrayList();
+		list.add("111");
+		list.add("222");
+		list.add(33);
+		list.add("444");
+		list.add(new Date());
+		list.add("666");
+		list.add("777");
+		list.add("888");
+		list.add("999");
+	}
+
+	@Test
+	public void testAdd() {
+		//测试add(Object obj)方法
+		list.add(100);
+		assertEquals(10, list.size());
+		
+		//测试add(int index, Object obj)方法
+		list.add(3, 444);
+		assertEquals(444, list.get(3));
+		
+		assertEquals("444", list.get(4));
+		assertEquals(11, list.size());
+	}
+	
+	@Test
+	public void testIsEmpty() {
+		
+		assertEquals(false, list.isEmpty());
+	}
+	
+	@Test
+	public void testGet() {
+		assertEquals(new Date(), list.get(4));
+	}
+	
+	@Test
+	public void testRemove() {
+	
+		// 测试remove(int index)方法
+		assertEquals(33, list.remove(2));
+		assertEquals("444", list.get(2));
+		
+		// 测试remove(Object obj)方法
+		assertEquals(true, list.remove("222"));
+		assertEquals("444", list.get(1));
+	}
+	
+	@Test
+	public void testSet() {
+		assertEquals(33, list.set(2, "333"));
+		assertEquals("333", list.get(2));
+	}
+
+}
diff --git a/group18/935542673/Coding/src/com/ikook/basic_data_structure/MyArrayList.java b/group18/935542673/Coding/src/com/ikook/basic_data_structure/MyArrayList.java
@@ -0,0 +1,158 @@
+package com.ikook.basic_data_structure;
+
+/**
+ * @author ikook;  QQ号码: 935542673
+ */
+public class MyArrayList implements MyList{
+
+	private Object[] elementData;
+	
+	private int size;
+	
+	/**
+	 * 使Object[]的长度默认为10；
+	 */
+	public MyArrayList() {
+		this(10);
+	}
+	 
+	/**
+	 * 在构造函数中初始化集合的长度
+	 * @param initialCapacity
+	 */
+	public MyArrayList(int initialCapacity) {
+		if(initialCapacity < 0) {
+			try {
+				throw new Exception();
+			} catch (Exception e) {
+				e.printStackTrace();
+			}
+		}
+		this.elementData = new Object[initialCapacity];
+	}
+
+	/**
+	 * 在集合中添加元素
+	 * @param obj
+	 */
+	public void add(Object obj) {
+		
+		ensureCapacity();
+		elementData[size++] = obj;
+		
+	}
+	
+	/**
+	 * 添加元素到集合的指定位置
+	 * @param index
+	 * @param obj
+	 */
+	public void add(int index, Object obj) {
+		rangeCheck(index);
+		ensureCapacity();
+	
+		System.arraycopy(elementData, index, elementData, index + 1, size-index);
+		elementData[index] = obj;
+		size++;
+	}
+	
+	/**
+	 * 返回集合的长度
+	 * @return
+	 */
+	public int size() {
+		return size;
+	}
+	
+	/**
+	 * 判断集合是非为空
+	 * @return
+	 */
+	public boolean isEmpty() {
+		return size == 0;
+	}
+	
+	/**
+	 * 获取集合指定位置的元素
+	 * @param index
+	 * @return
+	 */
+	public Object get(int index) {
+		rangeCheck(index);
+		return elementData[index];
+	}
+	
+	/**
+	 * 删除指定位置的对象
+	 * @param index
+	 */
+	public Object remove(int index) {
+		
+		rangeCheck(index);
+		
+		Object oldValue = elementData[index];
+		
+		int numMoved = size - index - 1;
+	    if (numMoved > 0){
+	   		System.arraycopy(elementData, index+1, elementData, index,
+                       numMoved);
+	    }
+	    elementData[--size] = null; 
+	    
+	    return oldValue;
+	}
+	
+	/**
+	 * 删除指定的对象(Object 对象)
+	 * @param obj
+	 */
+	public boolean remove(Object obj){
+		for(int i = 0; i < size; i++) {
+			if(get(i).equals(obj)) {
+				remove(i);
+				return true;
+			}
+		}
+		return false;
+	}
+	
+	/**
+	 * 更改集合中指定位置的元素，并返回原来的对象
+	 * @param index
+	 * @param obj
+	 * @return
+	 */
+	public Object set(int index, Object obj) {
+		rangeCheck(index);
+		
+		Object oldValue = elementData[index];
+		elementData[index] = obj;
+		
+		return oldValue;
+	}
+	
+	/**
+	 * 集合扩容封装类
+	 */
+	private void ensureCapacity() {
+		if(size == elementData.length) {
+			Object[] newArray = new Object[size * 2 + 1];
+			System.arraycopy(elementData, 0, newArray, 0, elementData.length);
+			elementData = newArray;
+		}
+	}
+	
+	/**
+	 * 判断集合范围是否越界的封装类
+	 * @param index
+	 */
+	private void rangeCheck(int index) {
+		if(index < 0 || index >= size) {
+			try {
+				throw new Exception("索引异常");
+			} catch (Exception e) {
+				e.printStackTrace();
+			}
+		}
+	}
+}
