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FAQ

FirstObject.jumpMustang();

⇐ 12345678910 ⇒



" !" println() (ln ) out System, java.lang. FirstProgram.java ( .java ), .

Package chapt01;

chapt01, . , , . package , . ( ), .

2 3 FirstProgram.java. .

( chapt01):

javac chapt01/FirstProgram.java

FirstProgram.class
Mustang.class. Java:

Java chapt01.FirstProgram

FirstProgram.class chapt01, .

, , java.sun.com. . JDK
( Windows) c:\jdk1.6.0, , Java , LASSPATH :

LASSPATH=.;c:\jdk1.6.0\

. , :\temp, .

, PATH

PATH=c:\jdk1.6.0\bin

javac.exe java.exe. JDK .

, . , . , . .

main(). , , String[] args. args[0] .. args.length.

/* # 4: : OutArgs.java */

package chapt01;

 

public class OutArgs {

public static void main(String[] args) {

for (String str: args)

System. out. printf("A-> %s%n", str);

}

}

Java 5.0 for Java printf().

for (int i = 0; i < args.length; i++)

System. out. println("A-> " + args[i]);

:

java chapt01.OutArgs 2007 Mustang "Java SE 6"

:

-> 2007

-> Mustang

-> Java SE 6

, , .

Java , , . C++: ; , , ; inline, C++, ; public, private, protected , , , , ++; private, . :

[] class [extends ]

[implements _]{/* */}

public ( ), final ( ), abstract ( , ). (friendly). . friendly . , - .

, extends, , implements. , .

// # 5: Java Beans : User.java

package chapt01;

public class User {

public int numericCode; //

private String password;

 

public void setNumericCode(int value) {

if (value > 0) numericCode = value;

else numericCode = 1;

}

public int getNumericCode() {

return numericCode;

}

public void setPassword(String pass) {

if (pass!= null) password = pass;

else password = "11111";

}

public String getPassword() {

//public String getPass() {//

return password;

}

}

User numericCode password, public private. password , setPassword(). numericCode User. public - .

/* # 6: ,

: UserView.java: Runner.java */

package chapt01;

 

class UserView {

public static void welcome(User obj) {

System. out. printf("! : %d, : %s",

obj.getNumericCode(), obj.getPassword());

}

}

public class Runner {

public static void main(String[] args) {

User user = new User();

user.numericCode = 71; // -

// user.password = null; //

user.setPassword("pass"); //

UserView. welcome (user);

}

}

:

! : 71, : pass

. . new , :

User user; //

user = new User(); //

:

User user = new User(); /* */

new , , . , .

, . , , equals(). Object, .

/* # 7: : ComparingStrings.java */

package chapt01;

 

public class ComparingStrings {

public static void main(String[] args) {

String s1, s2;

s1 = "Java";

s2 = s1; //

System. out. println(" "

+ (s1 == s2)); // true

//

s1 += '2';

// s1-="a"; //,

//

s2 = new String(s1);

System. out. println(" "

+ (s1 == s2)); // false

System. out. println(" "

+ s1.equals(s2)); // true

}

}

System.in . , , .

// # 8: System.in: DemoSystemIn.java

package chapt01;

 

public class ReadCharRunner {

 

public static void main(String[] args) {

int x;

try {

x = System. in. read();

char c = (char)x;

System. out. println(" : " + c + " =" + x);

} catch (java.io.IOException e) {

e.printStackTrace();

}

}

}

IOException, / , main()
try-catch.

. .

// # 9: : ReadCharRunner.java

package chapt01;

import java.io.*; //

 

public class ReadCharRunner {

 

public static void main(String[] args) {

/* System.in

InputStreamReader */

InputStreamReader is =

new InputStreamReader(System. in);

/* ,

*/

BufferedReader bis = new BufferedReader(is);

try {

System. out. println(

" <Enter>:");

/* ; readLine()

try */

String name = bis.readLine();

System. out. println(", " + name);

} catch (IOException e) {

System. err. print(" " + e);

}

}

}

, , :

<Enter>:

,

, , , .

, printf() Console.

/* # 10: printf() Console: PrintDeutsch.java */

public class PrintDeutsch {

public static void main(String[] args) {

String str = "über";

System. out. println(str);

Console con = System. console ();

con.printf("%s", str);

}

}

:

□ber

über

Java - , Web-. , , Web- .

// # 11: : FirstApplet.java

import java.awt.Graphics;

import java.util.Calendar;

public class FirstApplet extends javax.swing.JApplet {

private Calendar calendar;

 

public void init() {

calendar = Calendar. getInstance ();

setSize(250,80);

}

public void paint(Graphics g) {

g.drawString(" :", 20, 15);

g.drawString(

calendar.getTime().toString(), 20, 35);

}

}

Calendar java.util. toString() , , drawString(). , .

main() - init() paint(). HTML- Web-, Java. () <applet> HTML- view.html:

<html><body>

<applet code= FirstApplet.class width=300 height=300>

</applet></body></html>

FirstApplet.class , HTML-. HTML- Microsoft Internet Explorer - , Java.

view.html .1.4.

. 1.4.

JDK

appletviewer.exe.

1

A

1. Hello, , .

2. , main() .

3. , n .

4. -.

5. , () .

6. , , , . Calendar java.util.

7. HTML-.

B

n . :

1. .

2. .

3. , 3 9.

4. , 5 7.

5. , .

6. , .

7. .

8. .

9. .

10. .

11. .

12. : f0 = f1 = 1, f (n) = f (n1) + f (n2).

13. -, .

14. , .

15. p = m/n n m, .

16. .

1

1.1.

:

class Quest1 {

private static void main (String a) {

System.out.println("Java 2");

} }

, Quest1 ? ( 2 )

1) Quest1 public;

2) main() String[] a;

3) main() public;

4) main().

1.2.

Java: ( 2)

1) goto;

2) , ;

3) ;

4) ;

5) .

1.3.

:

class Quest3 {

public static void main(String s[ ]) {

String args;

System.out.print(args + s);

}

}

:

1) : main() ;

2) : args ;

3) : print();

4) .

1.4.

:

public class Quest4 {

public static void main(String[] args) {

byte b[]= new byte [80];

for (int i=0;i<b.length;i++)

b[i]=(byte)System.in.read();

System.out.print(Ok);

} }

:

1) : Ok;

2) , read() IOException;

3) , b
;

4) , .

1.5.

:

public class Quest5{

public static void main(){

System.out.print(""); }

public static void main(String args){

System.out.print(""); }

public static void main(String[] args){

System.out.print(""); } }

:

1) ;

2) ;

3) ;

4) ;

5) .

 
2

( ) . .

Java , (stack). . , -, , (heap).

, . Java . . .

() ( )
boolean   false true, false
byte     128..127
char   '\u0000' 0..65535
short     32768..32767
int     -2147483648..2147483647
long     922372036854775807L
float   0.0 3.40282347E+38
double   0.0 1.797693134486231570E+308

Java , : 35 , 071 , 051 . int. long, L (: 0xffffL). , int (2147483647), Java , long. 1.618 0.112E-05 double, , double. float, F. ('a', '\n', '\141', '\u005a'). Unicode, . Unicode , ASCII , C++. '\u code ', code . Java , ;

'\n' , '\r' , '\f' , '\t' , '\b' , '\uxxxx' Unicode, '\ddd' . J2SE 5.0 Unicode 4.0. Character.

true false, null . String . , , , .

byte à short à int à long à float à
double. Java byte short int . (). :

byte b = (byte)128; // int byte

, . , , -. Java , . (++), (--) (+=, /= ..). () .

, , # . $ _ , .

/* # 1: , :TypeByte.java */

package chapt02;

public class TypeByte {

public static void main(String[] args) {

byte b = 1, b1 = 1 + 2;

final byte B = 1 + 2;

//b = b1 + 1; //

/* b1 , b = b1 + 1; , b1 + 1 byte- */

b = (byte)(b1 + 1);

b = B + 1; //

/* B - , , B + 1, byte , */

//b = -b; //

b = (byte) -b;

//b = +b; //

b = (byte) +b;

int i = 3;

//b = i; // , int byte

b = (byte) i;

final int I = 3;

b = I; //

/*I . , byte, , */

final int I2 = 129;

//b=I2; // , .. 129 , 127

b = (byte) I2;

 

b += i++; //

b += 1000; //

b1 *= 2; //

float f = 1.1f;

b /= f; //

/* , . , b /= f; b = (byte)(b / f); */

}

}

, , , . , , . {}, .

Java /* */
//, , C++. /** */, :

@author ;

@version ;

@exception ;

@param , ;

@return , ;

@deprecated , ;

@since ( ) ;

@throws , ;

@see .

java-, , javadoc.exe
HTML-.

User .

package chapt02;

 

public class User {

/**

* personal user's code

*/

private int numericCode;

/**

* user's password

*/

private String password;

/**

* see also chapter #3 "Classes"

*/

public User() {

password = "default";

}

/**

* @return the numericCode

* return the numericCode

*/

public int getNumericCode() {

return numericCode;

}

/**

* @param numericCode the numericCode to set

* parameter numericCode to set

*/

public void setNumericCode(int numericCode) {

this. numericCode = numericCode;

}

/**

* @return the password

* return the password

*/

public String getPassword() {

return password;

}

/**

* @param password the password to set

* parameter password to set

*/

public void setPassword(String password) {

this. password = password;

}

}

HTML- :

. 2.1. User

Java C++ . Java , *, &, ->, delete . - . + += String. ==, != = , .
, .

: +, , *, %, /, ++, &, |, ^, ~ C++. , .

, , IEEE 754 +Infinity Infinity NaN (Not a Number), , , .

+ / ( )
+= ( ) /= ( )
% ( )
= ( ) %= ( )
* ++ ( )
*= ( ) ( )

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