diff --git a/src/class5/VariableDemo3.java b/src/class5/VariableDemo3.java
index 57a9ac4..e2ed9b0 100644
--- a/src/class5/VariableDemo3.java
+++ b/src/class5/VariableDemo3.java
@@ -5,7 +5,6 @@ public class VariableDemo3 {
         printVariable();
     }
     public static void printVariable(){
-        byte b = 10;
 
         short s = 20;
         int i = 30;
@@ -26,6 +25,5 @@ public class VariableDemo3 {
         System.out.println(l);
         System.out.println(i);
         System.out.println(s);
-        System.out.println(b);
     }
 }
diff --git a/src/class6/MethodDemo1.java b/src/class6/MethodDemo1.java
new file mode 100644
index 0000000..52d4520
--- /dev/null
+++ b/src/class6/MethodDemo1.java
@@ -0,0 +1,21 @@
+package class6;
+
+public class MethodDemo1 {
+    public static void main(String[] args) {
+        int sum = getSum(1,2);
+        System.out.println(sum);
+        System.out.println(getcode(4));
+    }
+    //定义一个方法，求任意两个证书的和并返回
+    public static int getSum(int a,int b){
+        return a+b;
+    }
+    public static String getcode(int len){
+        StringBuilder code = new StringBuilder();
+        for (int i = 0; i < len; i++) {
+            int number = (int)(Math.random()*10);
+            code.append(number);
+        }
+        return code.toString();
+    }
+}
diff --git a/src/class7/MethodDemo2.java b/src/class7/MethodDemo2.java
new file mode 100644
index 0000000..36f8c13
--- /dev/null
+++ b/src/class7/MethodDemo2.java
@@ -0,0 +1,24 @@
+package class7;
+
+public class MethodDemo2 {
+    public static void main(String[] args) {
+        print(1);
+        print(1.1);
+        print("hello world");
+
+
+    }
+    // 定义一个方法，打印一个整数
+    public static void print(int a){
+        System.out.println(a);
+    }
+    // 定义一个重载方法
+    public static void print(double a){
+        System.out.println(a);
+    }
+    // 定义一个重载方法
+    public static void print(String a){
+        System.out.println(a);
+    }
+
+}
diff --git a/src/class7/MethodDemo3.java b/src/class7/MethodDemo3.java
new file mode 100644
index 0000000..e80f587
--- /dev/null
+++ b/src/class7/MethodDemo3.java
@@ -0,0 +1,17 @@
+package class7;
+
+public class MethodDemo3 {
+    public static void main(String[] args) {
+        System.out.println(div(1,2));
+
+    }
+//    设计一个除法的功能
+    public static double div(double a,double b){
+        if (b==0){
+            return -1;
+        }
+        return a/b;
+    }
+
+}
+
diff --git a/src/class8/TypeDemo1.java b/src/class8/TypeDemo1.java
new file mode 100644
index 0000000..3581b04
--- /dev/null
+++ b/src/class8/TypeDemo1.java
@@ -0,0 +1,24 @@
+package class8;
+
+public class TypeDemo1 {
+    public static void main(String[] args) {
+        byte a =12;
+        print(a);
+        print2(a);
+
+        System.out.println("======================");
+        int i = 20;
+        print3((byte)i);
+
+    }
+    public static void print(int a){
+        System.out.println(a);
+    }
+    public static void print2(double a){
+        System.out.println(a);
+    }
+    public static void print3(byte j){
+        System.out.println(j);
+    }
+
+}