Java,java Data types

1. Java Development Kit Java SDK (contains many of our Java Runtime Libraries)

(1)JRE:Java Runtime Environment Java run-time environment

(2)Java: Development language

(3)Eclipse: Development tools myclipes idea

2, the class name to be the same as the file name to unify string s must be uppercase

Write a Java program output Helloworld

public class helloworld{

public static void Main (string[] args) {

System.out.println ("Helloworld");

}

}

The term of a program comes from life, usually the process of accomplishing certain things and things.

Java domain

Javase to do standard development

Java EE does server-side

Javame doing small-scale software development

Developing the application on the left

Developing programs on the internet side

Print ("") has no line-wrapping effect

println ("") has a line break effect

Program:

public class Helloworld {

public static void Main (string[] args) {

System.out.println ("Helloworld");

System.out.println ("Helloworld");

System.out.print ("Helloworld");

System.out.println ("Helloworld");

}

}

Operation Result:

Helloworld

Helloworld

Helloworldhelloworld

Java specification

Class names are decorated with public

One line is written with a single statement, ending with a semicolon.

Where to use {}

To indent

Write the program to achieve the following effect

public class Show {

public static void Main (string[] args) {

System.out.println ("My Name: the Prince of Tennis ");

System.out.println ("My hobby: playing tennis ");

}

}

Naming rules

Letters, numbers, underscores,$ and cannot start with numbers

Variable, attribute, method naming specification

Capital Initials -Hump rule

3. Data type

(1) basic data Types

Digital type

1, Integer type (byte, short,int,long)

2. Floating-point data type:float,double

Character type (char)

Boolean type (Boolean)

Data types are compared to the size of the storage space

BYTE, short(char),int,long,float,double

Coercion type conversions: Assigning a high-level data type to a lower-class data type must use a forced type conversion

Add the data type you want to convert before the data you want to convert

int i=768;

byte b= (byte) i;

The data type used to hold the character, takes 2 bytes, uses Unicode encoding, its first 128 byte encoding and ASCII compatible characters storage range in \u0000~\uffff, when defining the character type of data should pay attention to " , such as ' 1 ' denotes the character ' 1 ' instead of the value 1,

char c = ' 1 '; We try to output C to see,System.out.println (c), the result is 1, and if we output it System.out.println (c+0), the result becomes 49.

Java,java Data types