JAVA
Java
Java . Java ,
, -
. ,
Exception. ,
. ,
.
Java 5 : try,
catch, throw, throws
finally. .
(try) , ,
(throw) ,
(catch) (finally) .
.
try {
// }
catch (1 ) {
// 1 }
catch (2 ) {
// 2
throw(e)
// }
finally {
}
Delphi catch
except.
Throwable.
Throwable.
Throwable
. ception
,
. Throwable
Error, ,
.
-
Java .
, ,
.
class Exc0 {
public static void
main(string args[]) {
int d = 0;
int a = 42 / d;
} }
, .
:\> java Exc0
java.lang.ArithmeticException:
/ by zero
at Exc0.main(Exc0.java:4)
Exception Throwable.
Exception, : ArithmeticException, ,
. ,
, main.
class Exc1 {
static void
subroutine() {
int d = 0;
int a = 10 / d;
}
public static void
main(String args[]) {
Exc1.subroutine();
} }
,
Java .
:\> java Exc1
java.lang.ArithmeticException:
/ by zero
at
Exc1.subroutine(Exc1.java:4)
at
Exc1.main(Exc1.java:7)
try catch
,
, try. try-
catch, .
class Exc2 {
public static void
main(String args[]) {
try {
int d = 0;
int a = 42 / d;
}
catch
(ArithmeticException e) {
System.out.println("division
by zero");
}
}
}
catch-
, ,
(
division by zero).
catch
. ,
, Java catch-
try-. ,
,
. ,
catch
, Throwable.
class MultiCatch {
public static void
main(String args[]) {
try {
int a = args.length;
System.out.println("a = " + a);
int b = 42 / a;
int c[] = { 1 };
c[42] = 99;
}
catch
(ArithmeticException e) {
System.out.println("div
by 0: " + e);
}
catch(ArrayIndexOutOfBoundsException
e) {
System.out.println("array
index oob: " + e);
}
} }
, ,
.
,
, ,
ArrayIndexOutOf Bounds. ,
.
:\> java MultiCatch
= 0
div by 0:
java.lang.ArithmeticException: / by zero
array index oob:
java.lang.ArrayIndexOutOfBoundsException: 42
try
try
, .
try catch,
, ,
catch try. ,
try .
class MultiNest {
static void
procedure() {
try {
int c[] = { 1 };
c[42] = 99;
}
catch(ArrayIndexOutOfBoundsException
e) {
System.out.println("array
index oob: " + e);
} }
public static void
main(String args[]) {
try {
int a =
args.length();
System.out.println("a = " + a);
int b = 42 / a;
procedure();
}
catch
(ArithmeticException e) {
System.out.println("div
by 0: " + e);
}
} }
throw
throw
. , ,
Throwable, catch,
new. throw.
throw Throwable;
, .
try
catch. ,
. , try,
catch,
Java ,
. ,
-, throw
,
catch.
class ThrowDemo {
static void demoproc()
{
try {
throw new
NullPointerException("demo");
}
catch
(NullPointerException e) {
System.out.println("caught
inside demoproc");
throw e;
} }
public static void
main(String args[]) {
try {
demoproc();
}
catch(NulPointerException
e) {
System.out.println("recaught:
" + e);
}
} }
. main demoproc.
demoproc ,
NullPointerException throw
.
demoproc, - e.
, ,
throw,
main. ,
.
caught inside demoproc
recaught:
java.lang.NullPointerException: demo
throws
, ,
, .
, ,
throws.
(.. throw)
,
throws .
:
_(
) throws _ {}
,
procedure ,
, .
.
class ThrowsDemo1 {
static void
procedure() {
System.out.println("inside
procedure");
throw new
IllegalAccessException("demo");
}
public static void
main(String args[]) {
procedure();
} }
,
, , procedure
IllegalAccessException main
:
class ThrowsDemo {
static void
procedure() throws IllegalAccessException {
System.out.println("
inside procedure");
throw new
IllegalAccessException("demo");
}
public static void
main(String args[]) {
try {
procedure();
}
catch
(IllegalAccessException e) {
System.out.println("caught
" + e);
}
} }
.
inside procedure
caught
java.lang.IllegalAccessException: demo
finally
,
, .
finally. ,
catch,
finally , ,
try. try
catch finally. finally
,
. ,
,
finally.
class FinallyDemo {
static void procA() {
try {
System.out.println("inside
procA");
throw new
RuntimeException("demo");
}
finally {
System.out.println("procA's
finally");
} }
static void procB() {
try {
System.out.println("inside
procB");
return;
}
finally {
System.out.println("procB's
finally");
} }
public static void
main(String args[]) {
try {
procA();
}
catch (Exception e) {}
procB();
} }
procA -
try,
finally. procB
try- return,
finally. ,
.
:\> java FinallyDemo
inside procA
procA's finally
inside procB
procB's finally
Exception
Throwable
. int, char .., ,
Throwable, , String Object,
.
Exception.
, Exception.
class MyException
extends Exception {
private int detail;
MyException(int a) {
detail = a:
}
public String
toString() {
return
"MyException[" + detail + "]";
}
}
class ExceptionDemo {
static void
compute(int a) throws MyException {
System.out.println("called
computer + a + ").");
if (a > 10)
throw new
MyException(a);
System.out.println("normal
exit.");
}
public static void
main(String args[]) {
try {
compute(1);
compute(20);
}
catch (MyException e)
{
System.out.println("caught"
+ e);
}
} }
.
MyException Exception. ,
,
toString, , -.
ExceptionDemo compute,
MyExcepton. compute ,
- 10. main
compute ,
( 10),
. .
:\> java ExceptionDemo
called compute(1).
normal exit.
called compute(20).
caught MyException[20]
. Try, throw, catch
.
,
,
, , .
, - , , , , .
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