第一次作业

group09/715061147/.gitignore

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+.metadata
+.swp
+RemoteSystemsTempFiles/
+target

group09/715061147/mvnhomework1/.gitignore

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+.classpath
+.settings
+.project
+target

group09/715061147/mvnhomework1/pom.xml

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+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+	<modelVersion>4.0.0</modelVersion>
+	<groupId>com.qsq.study</groupId>
+	<artifactId>mvnhomework1</artifactId>
+	<version>0.0.1-SNAPSHOT</version>
+	<name>MvnHomeWork1</name>
+	<description>MvnHomeWork1</description>
+
+	<dependencies>
+		<dependency>
+			<groupId>junit</groupId>
+			<artifactId>junit</artifactId>
+			<version>4.12</version>
+		</dependency>
+	</dependencies>
+	<build>
+		<plugins>
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-compiler-plugin</artifactId>
+				<configuration>
+					<source>1.8</source>
+					<target>1.8</target>
+				</configuration>
+			</plugin>
+		</plugins>
+	</build>
+</project>

group09/715061147/mvnhomework1/src/main/java/com/qsq/study/ArrayList.java

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+package com.qsq.study;
+
+import java.util.Arrays;
+
+public class ArrayList<E> implements List<E> {
+
+	private static final int DEFAULT_CAPACITY = 16;
+	private static final Object[] EMPTY_ELEMENT_DATA = {};
+	private Object[] elementData;
+	private int size = 0;
+
+	/*
+	 * 构造一个默认容量的ArrayList
+	 */
+	public ArrayList() {
+		this(DEFAULT_CAPACITY);
+	}
+
+	/*
+	 * 构造一个指定初始容量的ArrayList
+	 * 
+	 * @param initialCapacity 初始容量
+	 * 
+	 * @throws IllegalArgumentException 指定初始容量为负数时抛出非法参数异常
+	 */
+	public ArrayList(int initialCapacity) {
+		if (initialCapacity > 0) {
+			this.elementData = new Object[initialCapacity];
+		} else if (initialCapacity == 0) {
+			this.elementData = EMPTY_ELEMENT_DATA;
+		} else {
+			throw new IllegalArgumentException("Illegal Capacity " + initialCapacity);
+		}
+	}
+
+	@Override
+	public int size() {
+		return this.size;
+	}
+
+	@Override
+	public boolean isEmpty() {
+		return size == 0;
+	}
+
+	/*
+	 * 增加elementData数组容量
+	 * 
+	 * @param capacity 新的数组容量
+	 */
+	private void grow(int capacity) {
+		if (capacity < elementData.length) {
+			return;
+		}
+		elementData = Arrays.copyOf(elementData, capacity);
+	}
+
+	@Override
+	public boolean add(E e) {
+		if (size == elementData.length) {
+			grow(size * 2);
+		}
+		elementData[size++] = e;
+		return true;
+	}
+
+	@Override
+	public E remove(int index) {
+		rangeCheck(index);
+
+		// move elements after index forward by 1
+		for (int i = index; i < size - 1; i++) {
+			elementData[i] = elementData[i + 1];
+		}
+		--size;
+
+		// TODO: JDK中实现: 1.效率 2.GC回收
+		// System.arraycopy(elementData, index + 1, elementData, index, size -
+		// index - 1);
+		// elementData[--size] = null;
+
+		return null;
+	}
+
+	@Override
+	public boolean remove(Object o) {
+		int index = indexOf(o);
+
+		if (index < 0) {
+			return false;
+		}
+
+		remove(index);
+		return true;
+	}
+
+	@SuppressWarnings({ "unchecked" })
+	private E elementData(int index) {
+		return (E) elementData[index];
+	}
+
+	private void rangeCheck(int index) {
+		// TODO: JDK源码中未对index<0的情况做处理，为何？
+		if (index < 0 || index >= size) {
+			throw new IndexOutOfBoundsException("Index:" + index + ", Size:" + size);
+		}
+	}
+
+	@Override
+	public E get(int index) {
+		rangeCheck(index);
+
+		return elementData(index);
+	}
+
+	@Override
+	public E set(int index, E element) {
+		rangeCheck(index);
+
+		E oldElement = elementData(index);
+		elementData[index] = element;
+		return oldElement;
+	}
+
+	@Override
+	public int indexOf(Object o) {
+		if (o == null) {
+			for (int i = 0; i < size; i++) {
+				if (elementData[i] == null) {
+					return i;
+				}
+			}
+		} else {
+			for (int i = 0; i < size; i++) {
+				if (o.equals(elementData[i])) {
+					return i;
+				}
+			}
+		}
+		return -1;
+	}
+
+}

group09/715061147/mvnhomework1/src/main/java/com/qsq/study/LinkedList.java

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+package com.qsq.study;
+
+public class LinkedList<E> implements List<E>{
+
+	private Node<E> first;
+	private Node<E> last;
+	private int size;
+
+	private static class Node<T> {
+		T item;
+		Node<T> prev;
+		Node<T> next;
+
+		public Node(Node<T> prev, T item, Node<T> next) {
+			this.prev = prev;
+			this.item = item;
+			this.next = next;
+		}
+	}
+
+	/*
+	 * 无参数构造函数
+	 */
+	public LinkedList() {
+		first = null;
+		last = first;
+		size = 0;
+	}
+
+	@Override
+	public int size() {
+		return this.size;
+	}
+
+	@Override
+	public boolean isEmpty() {
+		return size == 0;
+	}
+
+	private void rangeCheck(int index) {
+		if (index < 0 || index >= size) {
+			throw new IndexOutOfBoundsException("Index:" + index + ", Size:" + size);
+		}
+	}
+
+	@Override
+	public boolean add(E e) {
+		if (first == null) {
+			// 链表为空
+			first = new Node<E>(null, e, null);
+		} else if (last == null) {
+			// 尾结点为空
+			last = new Node<E>(first, e, null);
+			first.next = last;
+		} else {
+			Node<E> node = new Node<E>(last, e, null);
+			last.next = node;
+			last = node;
+		}
+		++size;
+		return true;
+	}
+
+	@Override
+	public boolean remove(Object o) {
+		int index = indexOf(o);
+		if (index < 0 || index > size) {
+			return false;
+		}
+
+		remove(index);
+		return true;
+	}
+
+	@Override
+	public E remove(int index) {
+		rangeCheck(index);
+
+		Node<E> current = first;
+		while (index > 0) {
+			--index;
+			if (current == null) {
+				return null;
+			}
+			current = current.next;
+		}
+
+		E oldItem = current.item;
+
+		if (current.prev == null) {
+			// 删除的是头结点
+			first = current.next;
+			if (current.next != null) {
+				current.next.prev = null;
+			}
+		} else {
+			current.prev.next = current.next;
+			if (current.next != null) {
+				current.next.prev = current.prev;
+			}
+		}
+		--size;
+
+		return oldItem;
+	}
+
+	@Override
+	public E get(int index) {
+		rangeCheck(index);
+
+		int i = 0;
+		Node<E> current = first;
+		while (i < index) {
+			if (current == null) {
+				return null;
+			}
+			++i;
+			current = current.next;
+		}
+		return current.item;
+	}
+
+	@Override
+	public E set(int index, E element) {
+		rangeCheck(index);
+
+		Node<E> current = first;
+		while (index > 0) {
+			--index;
+			current = current.next;
+		}
+		E oldElement = current.item;
+		current.item = element;
+
+		return oldElement;
+	}
+
+	@Override
+	public int indexOf(Object o) {
+		if (first == null) {
+			return -1;
+		}
+
+		Node<E> current = first;
+		int index = 0;
+		if (o == null) {
+			while (current != null) {
+				if (current.item == null) {
+					return index;
+				} else {
+					current = current.next;
+					++index;
+				}
+			}
+		} else {
+			while (current != null) {
+				if (o.equals(current.item)) {
+					return index;
+				} else {
+					current = current.next;
+					++index;
+				}
+			}
+		}
+
+		return -1;
+	}
+
+}

group09/715061147/mvnhomework1/src/main/java/com/qsq/study/List.java

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+package com.qsq.study;
+
+public interface List<E> {
+	int size();
+	boolean isEmpty();
+	boolean add(E e);
+	boolean remove(Object o);
+	E remove(int index);
+	E get(int index);
+	E set(int index, E element);
+	int indexOf(Object o);
+}