diff --git a/group04/1906242834/.classpath b/group04/1906242834/.classpath
new file mode 100644
index 0000000000..fb5011632c
--- /dev/null
+++ b/group04/1906242834/.classpath
@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<classpath>
+	<classpathentry kind="src" path="src"/>
+	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER"/>
+	<classpathentry kind="output" path="bin"/>
+</classpath>
diff --git a/group04/1906242834/.gitignore b/group04/1906242834/.gitignore
new file mode 100644
index 0000000000..ae3c172604
--- /dev/null
+++ b/group04/1906242834/.gitignore
@@ -0,0 +1 @@
+/bin/
diff --git a/group04/1906242834/.project b/group04/1906242834/.project
new file mode 100644
index 0000000000..a30533712f
--- /dev/null
+++ b/group04/1906242834/.project
@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<projectDescription>
+	<name>1906242834Learning</name>
+	<comment></comment>
+	<projects>
+	</projects>
+	<buildSpec>
+		<buildCommand>
+			<name>org.eclipse.jdt.core.javabuilder</name>
+			<arguments>
+			</arguments>
+		</buildCommand>
+	</buildSpec>
+	<natures>
+		<nature>org.eclipse.jdt.core.javanature</nature>
+	</natures>
+</projectDescription>
diff --git a/group04/1906242834/src/com/coding/basic/ArrayList.java b/group04/1906242834/src/com/coding/basic/ArrayList.java
new file mode 100644
index 0000000000..a4baff2fae
--- /dev/null
+++ b/group04/1906242834/src/com/coding/basic/ArrayList.java
@@ -0,0 +1,71 @@
+package com.coding.basic;
+
+public class ArrayList implements List {
+	
+	private int size = 0;
+	
+	private Object[] elementData = new Object[100];
+	
+	public void add(Object o){
+		//若插入元素后会溢出，则对数组进行扩容，在这里只把空间加1
+		if ((size()+1)>elementData.length) {
+			System.arraycopy(elementData, 0, elementData, 0, elementData.length+1);
+			elementData[size] = o;
+		}else {
+		//若插入元素后不出现溢出，则直接添加在末尾
+			elementData[size] = o;
+		}
+	}
+	//index在length范围之内正常插入，若index大于length则抛出异常
+	public void add(int index, Object o){
+		Object temp;
+		if (index<elementData.length) {
+			System.arraycopy(elementData, 0, elementData, 0, elementData.length+1);
+			temp = elementData[elementData.length-1];
+			elementData[elementData.length] = temp;
+			for (int i = elementData.length; i > index; i--) {
+				elementData[i-1] = elementData[i-2];
+			}
+			elementData[index] = o;
+		}else if (index==elementData.length) {
+			add(o);
+		}else{
+			System.out.println("ArrayIndexOutOfBoundsException");
+		}
+	}
+	
+	public Object get(int index){
+		if (index<=elementData.length-1) {
+			return elementData[index];
+		}else {
+			System.out.println("ArrayIndexOutOfBoundsException");
+		}
+		return elementData;
+	}
+	
+	public Object remove(int index){
+		if (index<elementData.length) {
+			for (int i = index; i < elementData.length; i++) {
+				elementData[i] = elementData[i+1];
+			}
+			return elementData;
+		}else {
+			System.out.println("ArrayIndexOutOfBoundsException");
+		}
+		return elementData;
+	}
+	
+	public int size(){
+		for (Object object : elementData) {
+			if (object!=null) {
+				size += 1;
+			}
+		}
+		return size;
+	}
+	
+	public Iterator iterator(){
+		return null;
+	}
+	
+}
\ No newline at end of file
diff --git a/group04/1906242834/src/com/coding/basic/BinaryTreeNode.java b/group04/1906242834/src/com/coding/basic/BinaryTreeNode.java
new file mode 100644
index 0000000000..dd29e233cc
--- /dev/null
+++ b/group04/1906242834/src/com/coding/basic/BinaryTreeNode.java
@@ -0,0 +1,5 @@
+package com.coding.basic;
+
+public class BinaryTreeNode {
+
+}
diff --git a/group04/1906242834/src/com/coding/basic/Iterator.java b/group04/1906242834/src/com/coding/basic/Iterator.java
new file mode 100644
index 0000000000..2cb041d8c1
--- /dev/null
+++ b/group04/1906242834/src/com/coding/basic/Iterator.java
@@ -0,0 +1,5 @@
+package com.coding.basic;
+
+public class Iterator {
+
+}
diff --git a/group04/1906242834/src/com/coding/basic/LinkedList.java b/group04/1906242834/src/com/coding/basic/LinkedList.java
new file mode 100644
index 0000000000..83c9478b71
--- /dev/null
+++ b/group04/1906242834/src/com/coding/basic/LinkedList.java
@@ -0,0 +1,5 @@
+package com.coding.basic;
+
+public class LinkedList {
+
+}
diff --git a/group04/1906242834/src/com/coding/basic/List.java b/group04/1906242834/src/com/coding/basic/List.java
new file mode 100644
index 0000000000..75b56eb40e
--- /dev/null
+++ b/group04/1906242834/src/com/coding/basic/List.java
@@ -0,0 +1,5 @@
+package com.coding.basic;
+
+public interface List {
+
+}
diff --git a/group04/1906242834/src/com/coding/basic/Queue.java b/group04/1906242834/src/com/coding/basic/Queue.java
new file mode 100644
index 0000000000..bf0c32a224
--- /dev/null
+++ b/group04/1906242834/src/com/coding/basic/Queue.java
@@ -0,0 +1,5 @@
+package com.coding.basic;
+
+public class Queue {
+
+}
diff --git a/group04/1906242834/src/com/coding/basic/Stack.java b/group04/1906242834/src/com/coding/basic/Stack.java
new file mode 100644
index 0000000000..133cbaebbe
--- /dev/null
+++ b/group04/1906242834/src/com/coding/basic/Stack.java
@@ -0,0 +1,35 @@
+package com.coding.basic;
+
+public class Stack {
+	private ArrayList elementData = new ArrayList();
+	
+	public void push(Object o){
+		for (int i = 0; i < elementData.size(); i++) {
+			if(elementData.get(i)==null){
+				elementData.add(i, o);
+			}
+		}
+	}
+	
+	
+	public Object pop(){
+		int length = elementData.size();
+		elementData.remove(length-1);
+		return elementData.get(length-1);
+	}
+	
+	public Object peek(){
+		int length = elementData.size();
+		return elementData.get(length-1);
+	}
+	public boolean isEmpty(){
+		if(elementData.size()==0){
+			return true;
+		}else{
+			return false;
+		}
+	}
+	public int size(){
+		return elementData.size();
+	}
+}
\ No newline at end of file