arrayList 0.1

luoziyihao · luoziyihao · commit b87fad9a98ab · 2017-02-25T15:54:54.000+08:00
diff --git a/group17/1204187480/code/homework/basic/src/main/java/com/coding/basic/ArrayList.java b/group17/1204187480/code/homework/basic/src/main/java/com/coding/basic/ArrayList.java
@@ -1,32 +1,85 @@
 package com.coding.basic;
 
+import java.util.Arrays;
+
 public class ArrayList implements List {
-	
-	private int size = 0;
-	
-	private Object[] elementData = new Object[100];
-	
-	public void add(Object o){
-		
-	}
-	public void add(int index, Object o){
-		
-	}
-	
-	public Object get(int index){
-		return null;
-	}
-	
-	public Object remove(int index){
-		return null;
-	}
-	
-	public int size(){
-		return -1;
-	}
-	
-	public Iterator iterator(){
-		return null;
-	}
-	
+
+    private int size = 0;
+
+    private Object[] elementData = new Object[100];
+
+    private int length() {
+        return elementData.length;
+    }
+
+    private static final int ENLARGE_LENGTH = 100;
+
+    private Object[] enlarge(Object[] origin) {
+        return Arrays.copyOf(origin, origin.length + ENLARGE_LENGTH);
+    }
+
+    private void enLargeElementData() {
+        if (size == length()) {
+            elementData = enlarge(elementData);
+        }
+    }
+
+    public void add(Object o) {
+        enLargeElementData();
+        elementData[size] = o;
+        size++;
+    }
+
+    public void add(int index, Object o) {
+        checkIndex(index);
+        enLargeElementData();
+        // 备份 index 处及后面的数据
+        Object[] elementsBehindIndex = backBehindElements(elementData, index);
+        // 给index处 设值
+        elementData[index] = o;
+        // 追加 备份的数据
+        appendElement(elementData, index, elementsBehindIndex);
+        size++;
+    }
+
+    private void appendElement(Object[] origin, int pos, Object[] append) {
+        System.arraycopy(append, 0, origin, pos, append.length);
+    }
+
+    private Object[] backBehindElements(Object[] elementData, int index) {
+        int backSize = size - index;
+        Object[] back = new Object[backSize];
+        System.arraycopy(elementData, index, back, 0, backSize);
+        return back;
+    }
+
+    public Object get(int index) {
+        checkIndex(index);
+        return elementData[index];
+    }
+
+    private void checkIndex(int index) {
+        if (index < 0 || index >= size) {
+            throw new ArrayIndexOutOfBoundsException(String.format("index=%s, size=%s", index, size));
+        }
+    }
+
+    public Object remove(int index) {
+        checkIndex(index);
+        Object[] back = backBehindElements(elementData, index + 1);
+        System.arraycopy(back, 0, elementData, index, back.length);
+        Object ret = elementData[index];
+        elementData[index] = null;
+        size--;
+        return ret;
+    }
+
+    public int size() {
+        return size;
+    }
+
+    public Iterator iterator() {
+        return null;
+    }
+
 }
diff --git a/group17/1204187480/code/homework/basic/src/test/java/com/coding/api/ArraysTest.java b/group17/1204187480/code/homework/basic/src/test/java/com/coding/api/ArraysTest.java
@@ -0,0 +1,22 @@
+package com.coding.api;
+
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.Arrays;
+
+/**
+ * Created by luoziyihao on 2/25/17.
+ */
+public class ArraysTest {
+    private final Logger logger = LoggerFactory.getLogger(this.getClass());
+
+
+    @Test
+    public void testCopyOf(){
+        Object[] a = new Object[]{1, 2, 3, 4};
+        Object[] b = Arrays.copyOf(a, 10);
+        logger.info("a={}, b={}", Arrays.toString(a), Arrays.toString(b));
+    }
+}
diff --git a/group17/1204187480/code/homework/basic/src/test/java/com/coding/api/SystemTest.java b/group17/1204187480/code/homework/basic/src/test/java/com/coding/api/SystemTest.java
@@ -0,0 +1,24 @@
+package com.coding.api;
+
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.Arrays;
+
+/**
+ * Created by luoziyihao on 2/25/17.
+ */
+public class SystemTest {
+
+    private final Logger logger = LoggerFactory.getLogger(this.getClass());
+
+        @Test
+    public void testArrayCopy() {
+        int[] a = new int[]{1, 2, 3, 4, 5, 6, 7};
+        int[] b = new int[]{11, 22, 33, 44, 55, 66, 77};
+        System.arraycopy(a, 2, b, 4, 3);
+        logger.info("b={}", Arrays.toString(b));
+
+    }
+}
diff --git a/group17/1204187480/code/homework/basic/src/test/java/com/coding/basic/ArrayListTest.java b/group17/1204187480/code/homework/basic/src/test/java/com/coding/basic/ArrayListTest.java
@@ -0,0 +1,35 @@
+package com.coding.basic;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+
+/**
+ * Created by luoziyihao on 2/25/17.
+ */
+public class ArrayListTest {
+
+    private final Logger logger = LoggerFactory.getLogger(this.getClass());
+
+
+    private List list = new ArrayList();
+
+    @Before
+    public void before() {
+
+    }
+
+    @Test
+    public void add() throws Exception {
+        list.add(1);
+    }
+
+    @Test
+    public void get() throws Exception {
+        add();
+        logger.info("{}", list.get(0));
+    }
+
+}
