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JAVA 章节二 基本数据类型目录 Java基本数据类型:两大类内置数据类型引用数据类型Java类型的转换自动类型转换强制类型转换Java的常量Java基本数据类型一、内置数据类型Java语言提供了八种基本类型。六种数字类型(四个整数型,两个浮点型),一种字符类型,还有一种布尔型。数值型--整数类型 byte:byte数据类型是8位、有符号的,以二进制补码表示的整数;最小值是-128(-2^7);最大值是127(2^7-1);默认值是0;byte类型用在大型数组中节约空间,主要代替整数,因为byte变量占用的空间只有int类型的四分之一;例子:byte a = 100,byte b = -50。数值型--整数类型 short:short数据类型是16位、有符号的以二进制补码表示的整数最小值是-32768(-2^15);最大值是32767(2^15 - 1);Short数
简介:JAVA 章节二 基本数据类型目录 Java基本数据类型:两大类内置数据类型引用数据类型Java类型的转换自动类型转换强制类型转换Java的常量Java基本数据类型一、内置数据类型Java语言提供了八种基本类型。六种数字类型(四个整数型,两个浮点型),一种字符类型,还有一种布尔型。数值型--整数类型 byte:byte数据类型是8位、有符号的,以二进制补码表示的整数;最小值是-128(-...
简介:一、char和varchar类型char和varchar类型类似,都用来存储字符串,但是它们保存和检索字符串的方式不同。char属于固定长度的字符类型,varchar属于可变长度的字符类型。例如:对于char(4)和varchar(4)这两种类型定义来说:(1)、''在char(4)中占了4个字节长度,varchar(4)则只占用一个字节的长度;(2)、'ab'在c...
简介:数据库表通常都会有一个字段类型为int,命名为id的自增主键。优点:使用int类型可自增,且比字符类型节省存储空间。 缺点:id是数值型,当要查询一个id对应的数据时,很难根据id判断是哪一个数据表。因此我们在存储时,应使用int,而在显示时对id进行一些处理,使很容易分辨这个id属于哪一个表。 编写了下面这个类,实现对id增加前缀及对已加前缀的id还原。Prefix.class.php<?...
简介:Character类的使用方法 Character:字符类型 1、属性。 static int MIN_RADIX :返回最小基数。 static int MAX_RADIX :返回最大基数。 static char MAX_VALUE :字符类型的最大值。 static char MIN_VALUE :字符类型的最小值。 static Class TYPE :返回当前类型。2、构造
Introduction: Common field type selection 1. It is recommended to use varchar/nvarchar data type for character type 2. It is recommended to use money data type for amount and currency 3. It is recommended to use numeric data type for scientific counting 4. It is recommended to use bigint for self-increasing identification Data type (the amount of data is too large to fit in the int type, and it will be troublesome to transform in the future) 5. The time type is recommended to be datetime data type 6. It is forbidden to use text, ntext, image and old data types 7. It is forbidden to use xml Data type, varchar(max), nvarchar(max)
6. Comprehensive understanding of data types in MySQL
Introduction: 1. Char and varchar types Char and varchar types are similar and are used to store strings, but they save and retrieve strings in different ways. char is a fixed-length character type, and varchar is a variable-length character type. For example: for the two type definitions of char(4) and varchar(4): (1), '' occupies 4 bytes in char(4), while varchar(4) only occupies one byte. Long
7. Python small function character type conversion method
Introduction: This article explains in detail the introduction of small functions for character type conversion of commonly used tools in python
8. JavaScript Object-Oriented Essentials (1)
Introduction: Data types In JavaScript, data types are divided into two categories: Primitive types store some simple data, such as true ,5 etc. There are 5 primitive types in JavaScript: boolean: Boolean, the value is true or false number: number, the value is any integer or floating point value string: string, the value is a single character or consecutive characters enclosed by single or double quotes (JavaScript does not distinguish between character types) null: empty type, which has only one value: null undefined: undefined, which has only one value: u..
9. Comparison between chr, unichr, ord character functions in Python
##Introduction: chr, unichr, ord They can all be used for character type conversion in Python. Here we will briefly talk about the comparison between chr, unichr, and ord character functions in Python. Friends in need can refer to
10. C# Learning Diary 10----Extra Chapter C Language Base Conversion
## Introduction: In C# Learning Diary 08---Character Type, I left a question: how to write a hexadecimal conversion program in C. Now I will eradicate this sequelae:
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