From a7627e56cb6740d2655af2fde9788f63b4499990 Mon Sep 17 00:00:00 2001
From: xuxin <840198532@qq.com>
Date: Wed, 14 Jan 2026 10:03:18 +0800
Subject: [PATCH] =?UTF-8?q?day02-=E6=95=B0=E6=8D=AE=E7=B1=BB=E5=9E=8B?=
 =?UTF-8?q?=E8=BD=AC=E6=8D=A2-=E8=87=AA=E5=8A=A8=E8=BD=AC=E6=8D=A2?=
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---
 day02/src/com/inmind/Demo01.java | 54 ++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)
 create mode 100644 day02/src/com/inmind/Demo01.java

diff --git a/day02/src/com/inmind/Demo01.java b/day02/src/com/inmind/Demo01.java
new file mode 100644
index 0000000..f0e3c33
--- /dev/null
+++ b/day02/src/com/inmind/Demo01.java
@@ -0,0 +1,54 @@
+package com.inmind;
+/*
+数据类型转换---自动转换
+自动转换：将取值范围小的类型自动提升为取值范围大的类型
+
+------------------------------------------------------
+
+自动类型转换顺序:byte、short、char---->int---->long---->float---->double
+
+在java，默认采用int来进行整数的计算！！！
+ */
+public class Demo01 {
+    public static void main(String[] args) {
+        //定义一个整数变量
+        //变量定义格式：
+        //数据类型 变量名 = 数据值;
+        int a = 20;
+        int b = 10;
+        //2个变量进行相加
+        int c = a+b;
+        System.out.println(c);//30
+
+        //定义一个字节型的变量
+        byte b1 = 2;
+        int sum = a + b1;//直接出现了自动类型转换，先将b1从1字节自动转换为4字节的int之后，再进行运算
+        System.out.println(sum);//22
+        System.out.println("-------------------------------------------");
+
+        //byte b2 = a + b1;//错误，a+b1发生了自动类型转换，结果是4字节不能直接赋值给1字节的byte
+        //定义一个short型的变量
+        short s = 10;
+        //定义一个int型变量
+        int i = 20;
+
+        int s1 = s+s;
+
+        //定义一个长整型
+        long l1 =  s+s;//将4字节的int赋值给了8字节的long，此时发生了自动类型转换
+        long l2 = 3L;//直接将8字节的值，赋值给了l2
+
+        //测试下整数赋值给浮点数时，就会发生自动类型转换
+        float f = 3.0F;
+        f = s;
+        f = i;
+        f = l1;
+        System.out.println(l1);
+        double d = 3.0;
+        d = s;
+        d = i;
+        d = f;//4字节float自动转换为了8字节的double
+        System.out.println(d);
+
+    }
+}