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Java Hello World

public class HelloWorld { /* Java * Hello World */ public static void main(String[] args) { System.out.println("Hello World"); // Hello World } }

[662E827A-FA32-4464-B0BD-40087F429E98.jpg]

HelloWorld.java
cmd C:\
javac HelloWorld.java cmd
java HelloWorld

Hello World

$ javac HelloWorld.java
$ java HelloWorld 
Hello World

-encoding utf-8

javac -encoding UTF-8 HelloWorld.java 
java HelloWorld

Gif

[java-HelloWorld.gif]

Java

Java Hello hello
MyFirstJavaClass
Java .java
Java public static void main(String[] args)

Java

A-Z a-z,$_
A-Z a-z,$_
age$salary_value__1_value
123abc-salary

Java

: default, public , protected, private
: final, abstract, static, synchronized

Java

Java 5.0 bug

class FreshJuice { enum FreshJuiceSize{ SMALL, MEDIUM , LARGE } FreshJuiceSize size; } public class FreshJuiceTest { public static void main(String[] args){ FreshJuice juice = new FreshJuice(); juice.size = FreshJuice.FreshJuiceSize.MEDIUM ; } }

Java


	private
	protected
	public
	default
	abstract
	class
	extends
	final
	implements
	interface
	native	Java
	new
	static
	strictfp
	synchronized
	transient
	volatile
	break
	case	switch
	continue
	do
	else
	for
	if
	instanceof
	return
	switch
	while
	assert
	catch
	finally
	throw
	throws
	try
	import
	package
	boolean
	byte
	char
	double
	float
	int
	long
	short
	super
	this
	void
	goto
	const

Java null true false

Java

C/C++Java

Java

public class HelloWorld { /* Java * Hello World * */ public static void main(String[] args){ // /* */ System.out.println("Hello World"); } }

Java

super classsub class

Java

[ZSSDMld.png]

Java Java

AI ...

Java

10

#0
Android
297***[email protected]
956
- (1) $
- (2)
- (3) java
jdk1.2strictfp() jdk1.4assert()jdk1.5enum()

truefalsenull
- (1)
- (2)
- (3) TarenaStudent
- (4) tarenaStudent
- (5) _
```
"\b" ()
"\f" ()
"\n" ()
"\r" ()
"\t" ((tab))
"\' " ()
"\" " () 
"\\" ()
```
Android
Android
297***[email protected]
9 (2017-08-10)
#0
   amy
  143***[email protected]
498
Java
boolean    1 8bit8
byte    1
char    2
short    2
int 4
float 4
long 8
double    8
Javaintlong Ll
floatfF
812562^8
2
amy
   amy
  143***[email protected]
9 (2017-09-28)

472

3 public class MyFirstClass{}

int index=0;
public void toString(){}

public static final String GAME_COLOR="RED";

1)$
2)
3)JAVA
4)

/**
* Copyright (C), 2006-2010, ChengDu Lovo info. Co., Ltd.
* FileName: Test.java
* 
*
* @author 
* @Date    
* @version 1.00
*/

/**  */
private String strMsg = null;

/**
* 
*
* @param 1 1
* @return 
* @throws . 
*/

/**
* 
*
* @param 1 1
* @throws . 
*/

//
Color bgColor = Color.RED

jinling9 (2018-01-07)

#0
   ycxchkj
  xch***163.com
205
Java

package: package com.runoob

classinterface: classinterfacePersonRuntimeException

class: ,indexcurrentImage

class : ,run()getBalance()

staticfinal: static finalPIPASSWORD

:

: byte[] buffer

ycxchkj
   ycxchkj
  xch***163.com
9 (2018-01-27)

233

Java

package
importimport
public classDefinitionJavaJava
classDefinition0
interfaceDefinition0

package javawork.helloworld;
/*classjavawork.helloworld*/
import java awt.*;
//AWT
import javawork.newcentury;
/*javawork.newcentury*/
 public class HelloWorldApp{...
/*HelloWorldApp*/ 
class TheFirstClass...;
//TheFirstClass 
interface TheFirstInterface{......}
/*TheFirstInterface*/

packageJavaJava

ID9 (2018-03-18)

#0
   admin
  125***[email protected]
216

Java

byte -128 - 127

byte b = 128;

byte b = 127+1;

-128

1
admin
   admin
  125***[email protected]
7 (2019-06-13)
#0
   hhh
  945***[email protected]

188
byte

Java byte -128~127-2^7~2^7-1

8 0 1

byte 1000 0000 0111 1111

Java

1

1000 000 1000 0000 0111 1111 1000 0000

byte -2^7=-128

0111 1111 2^7-1=127

byte 2^8=256 -128~127

char 0~2^16-165535
hhh
   hhh
  945***[email protected]

7 (2019-08-03)
#0

  198***[email protected]

155
throw throws
throws

throw

throws
throw try...catch throws

  198***[email protected]

6 (2020-09-11)
#0
   cxy
  597***[email protected]
50
1javajava.java.class
2.classjava(JVM)
3
cxy
   cxy
  597***[email protected]
4 (2022-08-29)

package 1;
public class {
public static void main(String[]args) {
    System.out.println("");
   }
}

4 (2022-12-12)

--

Java

Java

Java

Java

Java

Java

Java

Java

Java

Java

Java

Java

Java

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