diff --git a/Main.java b/Main.java
index 1a68b2dd0a36d3447eed91dc217b0ec3bb12c172..862e503cf8333492a59e1b296eade917b3e96abb 100644
--- a/Main.java
+++ b/Main.java
@@ -1,5 +1,34 @@
 class Main {
   public static void main(String[] args) {
-    System.out.println("Hello world!");
+    //变量基础的易错点
+    //1)变量的
+    long a = 10000000000L;  //long后面加F
+    System.out.println(a);
+    float b = 3.14F;        //float后加F
+    System.out.println(b);
+
+    //double的精度不足，输出时易发生误差
+    double c=3.14,d=7.62;
+    System.out.println(d-c);
+
+
+
+    //类型转换的易错点
+    byte a1,a2;
+    a1 = 5; a2 = 7;
+    //两个变量相加类型自动转为int类型需强转
+    byte a3 = (byte)(a1+a2);//括号内类型与前面一定要一致
+    System.out.println(a3);  
+
+    //变量的命名能用的有哪些
+    int _$a1 = 5;
+    //变量的命名只能用两种符号_、$字母和数字并且不能以数字开头
+    System.out.println(_$a1);
+
+
+    //输出的易错
+    int j = 1;
+    System.out.println("j");   //双引号内仅输出字符，与他的变量无关
+    System.out.println(j);     //输出1
   }
 }
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