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FAQ

DateFormat.getDateInstance();

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DateFormat.MEDIUM , . DateFormat LONG FULL. SHORT , .

String format(Date date) :

String dat = df.format(new Date());

Date parse(String source) , :

String str = "April 3, 2006";

Date d = df.parse(str);

, .

.

// # 18: : DemoDateFormat.java

package chapt07;

import java.text.DateFormat;

import java.text.ParseException;

import java.util.*;

 

public class DemoDateFormat {

public static void main(String[] args) {

DateFormat df =

DateFormat. getDateInstance (DateFormat.MEDIUM, Locale.US);

Date d = null;

String str = "April 3, 2006";

try {

d = df.parse(str);

System. out. println(d);

} catch (ParseException e) {

e.printStackTrace();

}

df =

DateFormat.getDateInstance(DateFormat.FULL,

new Locale("ru","RU"));

System. out. println(df.format(d));

 

df =

DateFormat.getDateInstance(DateFormat.FULL,Locale.GERMAN);

System. out. println(df.format(d));

 

d = new Date();

// df

df = DateFormat. getTimeInstance ();

//

System. out. println(df.format(d));

}

}

:

Mon Apr 03 00:00:00 EEST 2006

2006 .

Montag, 3. April 2006

05:45:16

, :

Date d = new Date();

Locale[] locales =

DateFormat.getAvailableLocales();

for (Locale loc: locales) {

DateFormat df =

DateFormat. getDateInstance (DateFormat.FULL, loc);

System.out.println(loc.toString() + "---> "

+ df.format(d));

}

, , loc.toString().

7

A

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25. Java (//, /*, /**).

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n m.

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31. , .

32. %user%%/user%
<a href=http://www.my.by/search.htm?param=></a>.

33. Java getter setter- , .

34.
.

B

1. , . , . , , .

2. , .

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25. , , , . , hellowoooorld hel2owo4rld.

26. , .

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28. , . .

29. , : 2 ABC, 3 DEF, 4 GHI, 5 JKL, 6 MNO, 7 PQRS, 8 TUV, 9 WXYZ. , , .

30. , , .. .

31. . , . , .

32. , . .

33. . , , , .

34. . . , StringBuffer?

35. . : , , . , JAVA JAVA, AVAJ, VAJA, AJAV. AJAV, AVAJ, JAVA, VAJA. , VJAA. .

36. . , VJAA, JAVA.

7

7.1.

:

public class Quest1 {

public static void main(String[] args) {

String str = new String("java");

int i=1;

char j=3;

System.out.println(str.substring(i,j));

}}

:

1) ja;

2) av;

3) ava;

4) jav;

5) : substring().

7.2.

, v str = "Java"?

1) charAt(2,str);

2) str.charAt(2);

3) str.indexOf('v');

4) indexOf(str,'v');

7.3.

?

String s = new String("Java");
String t = new String();
String r = null;

1) r = s + t + r;

2) r = s + t + r;

3) r = s & t & r;

4) r = s && t && r;

7.4.

:

public class Quest4 {

public static void main(String[] args) {

String str="ava";

char ch=0x74; // 74 - 'J'

str=ch+str;

System.out.print(str);

}}

:

1) 74ava;

2) Java;

3) 0H74ava;

4) : ch+str;

5) : char ch=0x74;

6) .

7.5.

?

public class Quest5 {

public static void main(String[] args) {

StringBuffer s = new StringBuffer("you java");

s.insert(2, "like ");

System.out.print(s);

}}

1) yolike u java;

2) you like java;

3) ylike ou java;

4) you java like;

5) ;

6) .

 

 

 
8

() , . : , . , . , . - , . , , , . , , , .

Throwable
Error
Exception
RuntimeException

. , . Throwable Error Exception java.lang.

. 8.1.

Error . ,
, . , Error, 8.2.

. 8.2. , Error.

8.3 , Exception.

, , throws - . .

, . 8.4. , RuntimeException . , . RuntimeException . , :

if(a==null) throw new NullPionterException();

NullPionterException . , throw. main(),
printStackTrace(), .

. 8.3. (checked)

:

try-catch ;

throws ( );

.

. CloneNotSupportedException. :

public void changeObject(Student ob) {

try {

Object temp = ob.clone();

//

} catch (CloneNotSupportedException e) {

System. err. print(e);

}

}

. 8.4. (unchecked)

, ( Cloneable). , catch, , catch . try . catch(){} , - .

. , , , . throws, . . :

(_)

throws _ { }

try-catch, . , changeObject() :

public void changeObject(Student ob)

throws CloneNotSupportedException {

Object temp = ob.clone();

//

}

throws , . , changeObject():

public void load(Student stud) {

try {

changeObject(stud);

} catch (CloneNotSupportedException e) {

String error = e.toString();

System. err. println(error);

}

}

.

try , catch, catch .

/* # 1: : TwoException.java */

package chapt08;

public class TwoException {

public static void main(String[] args) {

try {

int a = (int)(Math. random () * 2);

System. out. println("a = " + a);

int c[] = { 1/a };

c[a] = 71;

} catch (ArithmeticException e) {

System. err. println(" 0" + e);

} catch (ArrayIndexOutOfBoundsException e) {

System. err. println(

" : " + e);

} // catch

System. out. println(" try-catch");

}

}

" 0" =0. ( =1) " " [], . , , , . , if . , , .

catch , . :

try { /*, */

} catch (RuntimeException e) { /* RuntimeException

*/

} catch (ArithmeticException e) {} /* ,

*/

try . try catch, , , catch try.

/* # 2: try-catch: MultiTryCatch.java */

package chapt08;

public class MultiTryCatch {

public static void main(String[] args) {

try { //

int a = (int) (Math. random () * 2) - 1;

System. out. println("a = " + a);

try { //

int b = 1/a;

StringBuffer sb = new StringBuffer(a);

} catch (NegativeArraySizeException e) {

System. err. println(

" : " + e);

}

} catch (ArithmeticException e) {

System. err. println(" 0" + e);

}

}

}

a=0 ArithmeticException, trycatch . .

.

throw

, , , , . throw, - , . throw . Throwable , . throw, :

throw Throwable;

- new:

throw new IOException();

throw . try catch. , , try. - throw .

, -, throw , catch,
.

/* # 3: : ThrowGeneration.java */

package chapt08;

import java.io.File;

public class ThrowGeneration {

public static void connectFile(File file) {

if (file == null ||!file.exists())

throw new IllegalArgumentException(); /*

*/

//

}

public static void main(String[] args) {

File f = new File("demo.txt");

// File f = null;

try {

connectFile (f);

} catch (IllegalArgumentException e) {

System. err. print(" unchecked-"

+ " : " + e);

}

}

connectFile() ( null) , . IllegalArgumentException, RuntimeException, main().

throws.

throw catch , (checked) throws . , RuntimeException (unchecked) , throws .

finally

, ( , ) , . finally, try catch. :

try { /*, */ }

catch (Exception1 e1) { /* 1*/ } //

catch (Exception2 e2) { /* 2*/ } //

finally { /* try, catch */ }

try catch finally. finally , . , return, break, continue. :

/* # 4: finally: StudentFinally.java */

package chapt08;

 

public class StudentFinally {

private static int age;

public static void setAge(int age) {

try {

//

if (age <= 0)

throw new RuntimeException(" ");

} finally {

System. out. print(" ");

//

}

System. out. print(" ");

}

public static int getAgeWoman() {

try {

return age - 3;

} finally {

return age;

}

}

public static void main(String[] args) {

try {

setAge (23);

setAge (-5);

} catch (RuntimeException e) {

e.printStackTrace();

}

System. out. print(getAgeWoman ());

}

}

setAge() - try, finally. getAgeWoman()
try return, finally.

Exception , , . , Human () age ().

/* # 5: , , :

RunnerLogic.java */

package chapt08;

public class RunnerLogic {

public static double salary(int coeff)

throws SalaryException {

double d;

try {

if ((d = 10 - 100/coeff) < 0)

throw new SalaryException("negative salary");

else return d;

} catch (ArithmeticException e) {

throw new SalaryException("div by zero", e);

}

}

public static void main(String[] args) {

try {

double res = salary (3); // 0, 71;

} catch (SalaryException e) {

System. err. println(e.toString());

System. err. println(e.getHiddenException());

}

}

}

ArithmeticException, , , SalaryException, . . - , ; - , . , . , SalaryException, getHiddenException(). , SalaryException.

/* # 6: : SalaryException.java */

package chapt08;

public class SalaryException extends Exception {

private Exception _hidden;

 

public SalaryException(String er) {

super (er);

}

public SalaryException(String er, Exception e) {

super (er);

_hidden = e;

}

public Exception getHiddenException() {

return _hidden;

}

}

, . .

. :

throws , ;

throws throws , .

. throws . , , , . checked- .

/* # 7: : Stone.java: WhiteStone.java: BlackStone.java: StoneLogic.java */

package chapt08;

class Stone { //

public void build() throws FileNotFoundException {

/* */ }

}

class WhiteStone extends Stone { //

public void build() {

System. out. println(" ");

}

}

public class StoneLgic { //

public static void infoStone(Stone stone) {

try {

stone.build(); // IOException

} catch (FileNotFoundException e) {

System. err. print(" ");

}

}

}

class BlackStone extends Stone { //

public void build() throws IOException{ //

System. out. println(" ");

/* */

}

}

throws , , throws

.

/* # 8: : FileInput.java: SocketInput.java */

package chapt08;

import java.io.FileNotFoundException;

import java.io.IOException;

 

class FileInput { //

public FileInput(String filename)

throws FileNotFoundException {

//

}

}

class SocketInput extends FileInput {

//

public SocketInput(String name)

throws FileNotFoundException {

super (name);

//

}

/

public SocketInput() throws IOException {

super ("file.txt");

//

}

/

public SocketInput(String name, int mode) { /*

*/

super (name);

//

}

}

, throws. , FileInput , .

assertion

. . , , , (, ), . .. (assertion). , .

:

int age = ob.getAge();

if (age >= 0) {

//

} else {

//

}

assertion , :

int age = ob.getAge();

assert (age >= 0): "NEGATIVE AGE!!!";

//

assert:

assert ( boolexp ): expression;

assert ( boolexp );

boolexp boolean Boolean, expression , . false, AssertionError, expression ( ).

assertion , , :

enum Mono { WHITE, BLACK }

String str = "WHITE"; //"GRAY"

Mono mono = Mono.valueOf(str);

//

switch (mono) {

case WHITE: //

break;

case BLACK: //

break;

default:

assert false: "Colored!";

}

assertion public -. : IllegalArgumentException, NullPointerException . assertion , .

Assertion :

java enableassertions MyClass

java ea MyClass

da -disableassertions.

8

A

4, /. , , . , , () , ..

B

4, /.

8

8.1.

:

class Quest1{

int counter;

java.io.OutputStream out;

Quest1(){/* out */}

float inc() {

try { counter++;
out.write(counter); }

//

}}

inc() , ? ( ).

1) catch (java.io.OutputStreamException e){};

2) catch (java.io.IOException e){};

3) catch (java.io.OutputException e){};

4) finally{};

5) return counter;

6) return;.

8.2.

meth(5)?

public int meth(int x) {

int y = 010; //1
try { y += x; //2

if (x<=5) throw new Exception(); //3

y++; } //4
catch (Exception e) { y--; } //5

return y; } //6

1) 12;

2) 13;

3) 14;

4) 15;

5) : 4.

8.3.

meth(12), mexcept(int x) ArithmeticException?

int meth(int x) {

int count=0;

try { count += x;

count += mexcept(count);

count++;

} catch (Exception e) {

--count;

return count;

}

finally {

count += 3;

return count;

}

}

1) 11;

2) 12;

3) 13;

4) 14;

5) - return finally.

8.4.

show() // Quest4?

class Base{

public void show(int i) {/**/}
}
public class Quest4 extends Base{
//
}

1) void show (int i) throws Exception {/**/}

2) void show (long i) throws IOException {/**/}

3) void show (short i){ /**/}

4) public void show (int i) throws IOException {/**/}

8.5.

:

import java.io.*;

public class Quest5 {

// ioRead()

public static void main(String[] args) {

try {

ioRead();

} catch (IOException e){}

}}

ioRead() , ?

1) private static void ioRead()

throws IOException{};

2) public static void ioRead()

throw IOException{};

3) public static void ioRead(){};

4) public static void ioRead()

throws Exception{}.

 
9

. /

/ , . . / .

File

(), , Java java.io.

File . , , , , , , , ..

File :

File myFile = new File(\\com\\myfile.txt);

File myDir = new File(c:\\jdk1.6.0\\src\\java\\io);

File myFile = new File(myDir, File.java);

File myFile = new File(c:\\com, myfile.txt);

File myFile = new File(new URI( - ));

, , . . . ,
.

File .

, : Unix / , Windows \\ . , , , File:

public static final String separator;

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==> ...

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