exception handling examples

7/24/2019 Exception Handling Examples

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Exception Handling Examples

Exception in java with Example Program

1. Exception

An exception is a problem that arises during the execution of a program

Exception is a runtime error

An exception can occur for many different reasons, including the following:

A user has entered invalid data.

A file that needs to be opened cannot be found.

A network connection has been lost in the middle of communications, or the JVM has run out of memory.

Types of error:

Compile time error

Compile time error is any type of error that prevent a java program compile like a syntax error, a class not found, a bad file name for the defined

class, and so on.

Run time error

A runtime error means an error which happens, while the program is running. To deal with this kind of errors java define Exceptions. Exceptions

are objects represents an abnormal condition in the flow of the program. It can be either checked or unchecked.

1.2 Types of exception

Checked Exceptions

Errors

Runtime Exceptions

Checked Exception( handled at compile time.)

Environmental error that cannot necessarily be detected by testing; e.g. disk full, broken socket, database unavailable, etc. The Exception problemcan be overcome by implementing Try-Catch block.

Error

Virtual machine error: class not found, out of memory, no such method, illegal access to private field, etc

Runtime Exception(Unchecked Exception)

Programming errors that should be detected in testing: index out of bounds, null pointer, illegal argument, etc.

The Compiler never checks the Unchecked exception during the program compilation. For example, Dividing any number by zero is an unchecked

exception.

1.3Exception Hierarchy

1.4 Exception management

Exception can be managed through five keywords in java

1.try

2.catch

3.finally

4.throw

5.throws

try-used to keep the code that going to throw error

catch-used to catch and process the error thrown by try block

example for try /catch block:


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classSam

{

publicstaticvoidmain(String args[])

{

intk=0;

intmsg;

String s1=args[0];

String s2=args[1];

inti=IntegerparseInt(s1);

int!=IntegerparseInt(s2);

tr"

{

k=i#!;

S"stemoutprintln(k);

$

catc%(&'ception e)

{

S"stemoutprintln(error);

$

$

finally-A finally block of code always executes, whether or not an exception has occurred. Finally used for avoid resource leakage .

The finally clause is executed after a try-catch block has been executed .

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tr"{##*rotected code$catc%(&'ception+"pe1 e1){

##,atc% block$catc%(&'ception+"pe2 e2){
http://candidjava.com/exception-in-java-with-example-program/http://candidjava.com/exception-in-java-with-example-program/http://candidjava.com/exception-in-java-with-example-program/http://candidjava.com/exception-in-java-with-example-program/


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##,atc% block$catc%(&'ception+"pe- e-){##,atc% block

$.inall"{##+%e .inall" block al/a"s e'ecutes$

Example for finally:

?

1,onnection conn; ## opened be.ore at t%e beginning o.t%e met%od

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tr"{## e'ecute a uer"$ catc%(S3&'ception e) {## %andles t%e e'ception dispal"ing a message /%atever$ .inall"{connclose();$

throw-throwis used to actually throw the exception

throws-throwsis declarative for the method. They are not interchangeable.

The following code shows how to handle multiple exceptions using thethrowskeyword.

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2021

publicclass&'ample{ publicvoide'ception&'ample() { tr" { ## statements c%eck(); $ catc%(&'ception e)

{ ##statements $ $ ## multiple e'ceptions separated b" a comma

voidc%eck() t%ro/s4ull*ointer&'ception4egative5rra"Si6e&'ception { i.(.lag 7 0) t%ro/ne/4ull*ointer&'ception(); i.(arrsi6e 7 0) t%ro/ne/4egative5rra"Si6e&'ception();

$$
http://candidjava.com/exception-in-java-with-example-program/http://candidjava.com/exception-in-java-with-example-program/http://candidjava.com/exception-in-java-with-example-program/http://candidjava.com/exception-in-java-with-example-program/http://candidjava.com/exception-in-java-with-example-program/http://candidjava.com/exception-in-java-with-example-program/


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Primarykey

This tutorial explains how to set a primary key for a table in mysql using java statement example, Load the mysql driver using Class.forName

method and create a connection to communicate with mysql database and then create a statement object to send and receive from java code and

use executeUpdate to execute the query. If we wants to change a column constrain to primary key using java use this tutorial

Java code:

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import!avasl,onnection;

import!avasl8river9anager;

import!avaslS3&'ception;

import!avaslStatement;

publicclass*rimar"ke" {

#::

: param args

:#

publicstaticvoidmain(String[] args) {

## +comm"sl!dbc8river>;

String url = >!dbc?m"sl?##local%ost#test>;

String u4ame =>root>;

String p/d = >root>;

,onnection conn=null;

tr"{

,lass.or4ame(8river)ne/Instance();

conn = 8river9anagerget,onnection(url
http://candidjava.com/statement-primary-key-example-program-in-java-jdbc-mysql-database/http://candidjava.com/statement-primary-key-example-program-in-java-jdbc-mysql-database/


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u4ame p/d);

Statement stmt = conncreateStatement();

String sl = >5lter table student 5dd

primar" ke" (@ollA4o)>;

stmte'ecuteBpdate(sl);

S"stemoutprintln(>primar"ke" added

sucess.ull">);

$ catc%(,lass4otCound&'ception e) {

## +


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$

Output:

Unique statement:

This tutorial explains how to update a column constrainto unique in a table in mysql using java statement example, Load the mysql driver using

Class.forName method and create a connection to communicate with mysql database and then create a statement object to send and receive

from java code and use executeUpdate to execute the query.

Java code:

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import!avasl@esultSet;



publicclassBniue {

#::

: param args

:#



String url = >!dbc?m"sl?##local%ost#sec>;


http://candidjava.com/statement-unique-example-program-in-java-jdbc-mysql-database/http://candidjava.com/statement-unique-example-program-in-java-jdbc-mysql-database/


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tr"{


conn = 8river9anagerget,onnection(url u4ame p/d);


String sl = >create table student2(rollAno int 4create table sucess.ull">);


## +


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$

$

$

Output:

Create statement:

This tutorial explains how to Create a table in mysql using java statement example, Load the mysql driver using Class.forName method and create

a connection to communicate with mysql database and then create a statement object to send and receive from java code and use

executeUpdate to execute the query . The following codes in this java tutorial explain how to Create a table named staff with columns as Fields,

Type, Null, Key, Default, Extra .

Java code:

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import!avasl@esultSet;



publicclass,reate+able {

#::

: param args

:#

http://candidjava.com/statement-create-table-example-program-in-java-jdbc-mysql-database/http://candidjava.com/statement-create-table-example-program-in-java-jdbc-mysql-database/


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tr"{


conn = 8river9anagerget,onnection(url u4ame p/d);


String sl = >create table sta..(name varc%ar(2D)department

varc%ar(D)sub!ectAname varc%ar(2D))>;


S"stemoutprintln(>,reate+able sucess.ull">);


## +


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tr"{

connclose();

$ catc%(S3&'ception e) {

## +


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5 uer"


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u4ame p/d);


String sl = >delete .rom student /%ere

name=HraviH>;


S"stemoutprintln(>8ata deleted

sucess.ull">);


## +


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$

OUTPUT:

Data deleted successfully

SQ I!S"#T I!TO Statement:

This tutorial explains how to insert a single row into a table in mysql using java statement example, Load the mysql driver using Class.forName


use executeUpdate to execute the query. If we wants to add a new record into the table or to add a new row, just use this following code to

update the table with new record.

create table:

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createtablestudent(@ollA4o int(D)4amevarc%ar(2D)

8epartment varc%ar(E)5ddress varc%ar(-0));

uer"


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Java code:

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publicclass,reate+able {

#::

: param args

:#







tr"{



u4ame p/d);

Statement st= conncreateStatement();

String sl=>insert into student

values(H101HHsures%HHcseHHc%ennaiH)>;

ste'ecuteBpdate(sl);

S"stemoutprintln(>8ata Inserted

sucess.ull">);
http://candidjava.com/statement-insert-example-program-in-java-jdbc-mysql-database/http://candidjava.com/statement-insert-example-program-in-java-jdbc-mysql-database/


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## +


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Data Inserted successfully

$lter statement:

This tutorial explains how to alter a table in mysql using java statement example, Load the mysql driver using Class.forName method and create aconnection to communicate with mysql database and then create a statement object to send and receive from java code and use executeUpdate

to execute the query . While creating student table there is only four columns namely Roll_NO, Name, Department, Address. The following codes

in this java tutorial explain how to alter a table and create a new column.

create table:

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uer"


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publicclass5lter {

#::

: param args

:#







tr"{



u4ame p/d);


String sl = >5lter table student 5dd

8ateAo.Abirt% date>;


S"stemoutprintln(>table 5ltersucess.ull">);


## +


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## +


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Update statement:

This tutorial explains how to update a existing row in a table in mysql using java statement example, Load the mysql driver using Class.forName


use executeUpdate to execute the query. Use update query to update a existing data in a table this will be helpful in modifying record in a table.

create table:

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uer"


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connclose();

$ catc%(S3&'ception e) {

## +


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uer"


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tr"{



u4ame p/d);


@esultSet rs = stmte'ecuteuer"(>S&3&,+ :

C@);

S"stemoutprintln(>select statement

sucess.ull" used>);

/%ile(rsne't()) {

String @ollAno=

rsgetString(>@ollAno>);

String name= rsgetString(>name>);

String department=

rsgetString(>department>);

String address=

rsgetString(>address>);

S"stemoutprint(@ollAnoJ >Kt>);

S"stemoutprint(nameJ >Kt>);

S"stemoutprint(departmentJ >Kt>);

S"stemoutprintln( addressJ >Kt>);

$


## +


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catc%(&'ception e) {

## +


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#::

: aut%or candid!ava

: description?Lu..eredInputStream e'ample program .or

close() in !ava

:#

import!avaioCile;

import!avaioLu..eredInputStream;

import!avaioCileInputStream;

import!avaioCile4otCound&'ception;

import!avaioI&'ception /%ile reading

t%e .ile >J ioe);

$ .inall"{


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tr"{

i.(bin N= null)

binclose();

$ catc%(I


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publicstaticvoidmain(String[] args) t%ro/s&'ception

{

tr"{

String s=>candid>;##get t%e string

3ong l=ne/3ong(2OG);##get t%e long value

S"stemoutprintln(lvaluecandid>;##get t%e string


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S"stemoutprintln(3ongvalue


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{

S"stemoutprintln(n.eget9essage());##to print t%e e'ception massage

$

$

$

class8ee ##sub class

{

8ee(){$

void8ee() t%ro/s4umberCormat&'ception

{$

$

output

)*+

!ileOutputStream example program for get!"() () in java

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#::

:aut%or? candid!ava

:description? Cile


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Cile8escriptor .d = null;

booleanbool = .alse;

tr"{

## create ne/ .ile output stream

.os = ne/Cile,?##testt't>);

## get .ile descriptor instance

.d = .osgetC8();

## test i. t%e .ile is valid

bool = .dvalid();

## print

S"stemoutprint(>Is .ile validQ >J bool);

$ catc%(&'ception e') {

## i. an error occurs

e'printStack+race();

$ .inall"{

i.(.os N= null)

.osclose();

$

$

$

Output

is file valid? true

!ileInputStream example program for s#ip(long n) in java

1

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#::

:aut%or? candid!ava


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:description?

::#

import!avaioI,%aracter read? >J c);


## i. an" error occurs


$ .inall"{

## releases all s"stem resources .rom t%e

streams

i.(.is N= null)

.isclose();

$


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$

$

Output

Character read: E

!ileOutputStream example program for write(int $) () in java

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#::

:aut%or? candid!ava

:description? Cile);


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## /rites b"te to t%e output stream

.os/rite(b);

## .lus%es t%e content to t%e underl"ing

stream

.os.lus%();

## create ne/ .ile input stream

.is = ne/CileInputStream(>,?##testt't>);

## read till t%e end o. t%e .ile

/%ile((i = .isread()) N= 1) {

## convert integer to c%aracter

c = (c%ar) i;

## prints

S"stemoutprint(c);

$


## i. an error occurs


$ .inall"{

## closes and releases s"stem resources

.rom stream

i.(.os N= null)

.osclose();

i.(.is N= null)

.isclose();

$

$

$

Output

B


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!ileInputStream example program for close() in java

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#::

program ? CileInputStream e'ample program .or close()

in !ava

aut%or ? >candid>

date ? 2R1012

:#


import!avaioI5vailable ?>Javailable);

S"stemoutprintln(> @ead ?>J c);

$

$ catc%(&'ception e) {

eprintStack+race();


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$ .inall"{

i.(.is N= null) {

.isclose();

$

$

$

$

Output

Available :5 Read :K

Available :4 Read :AAvailable :3 Read :R

Available :2 Read :T

Available :1 Read :H

Available :0 Read :I

BufferedInputStream example program for s#ip(long n) in java

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#::

program ? Lu..eredInputStream e'ample program .or

skip(long n) in !ava

aut%or ? >candid>

date ? 211112

:#

##!ava code



import!avaioCilterInputStream;

import!avaioI


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publicstaticvoidmain(String[] args) t%ro/s&'ception {

InputStream is = null;

CilterInputStream .is = null;

inti = 0;

c%arc;

tr"{

is = ne/CileInputStream(>C?#kart%i#LIStreamSkip#kart%it't>);##

kart%it't

## content?kart%i

.is = ne/Lu..eredInputStream(is);

/%ile((i = .isread()) N= 1) {

c = (c%ar) i;

.isskip(-);

S"stemoutprintln(>,%aracter read? >J c);

$

$ catc%(I


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BufferedInputStream example program for reset() in java

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#::

: aut%or? candid!ava

: description? in P5M5 e'ample program .or

:#



import!avaioI,%ar ? >J (c%ar)bisread());

S"stemoutprintln(>,%ar ? >J (c%ar)

bisread());


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## mark is set on t%e input stream

bismark(0);

S"stemoutprintln(>,%ar ? >J (c%ar)bisread());

S"stemoutprintln(>reset() invoked>);

## reset is called

bisreset();

## read and print c%aracters




eprintStack+race();

$ .inall"{

## releases an" s"stem resources associated

/it% t%e stream

i.(iStream N= null)

iStreamclose();

i.(bis N= null)

bisclose();

$

$

$

Output

Char : A

Char : B

Char : C

Char : D

reset() invoked

Char : D

Char : E


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%hread Example program for run()

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## +%read &'ample *rogram .or run()

#::

aut%or? ,andid!avacom

description? +%is program runs t%e run() met%od .irst

t%en e'ecutes t%e main met%od

:#

publicclass4e/ implements@unnable

{

publicvoidrun() ## run met%od starts %ere

{

tr"{

.or(inti=0;i711;iJJ)

{

S"stemoutprintln(i);

+%readsleep(1000); ##/aiting .or one second

$

$

catc%(&'ception e){$

$

publicstaticvoidmain(String a[])

{

4e/ n=ne/4e/(); ## creating a ne/ ob!ect

+%read t1=ne/+%read(n); ## creating a t%read ob!ect

t1run(); ## starting t%e run met%od

tr"{


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.or(int!=11;!721;!JJ)

{

S"stemoutprintln(!);

+%readsleep(1000);

$

$

catc%(&'ception e){$

$

$

output:

,

-

.

/

+

)

*

0

1

2-,

--

-.

-/

-+

-)

-*

-0

-1

-2

.,

&ava Program used to get the pathname of the file using getPath() method

Get Filepath program to get the pathname of the file.

"3ample Pro&ram

?

1 packageservice1;
http://candidjava.com/java-program-used-to-get-the-pathname-of-the-file-using-getpath-method/http://candidjava.com/java-program-used-to-get-the-pathname-of-the-file-using-getpath-method/


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import!avaioCile;

publicclassStrCilepat% {


Cile . = null;

String v;

booleanbool = .alse;

tr"{

## create ne/ .ile

. = ne/Cile(>testt't>);

## pat%name string .rom abstract pat%name

v = .get*at%();

## true i. t%e .ile pat% e'ists

bool = .e'ists();

## i. .ile e'ists

i.(bool) {

## prints

S"stemoutprint(>pat%name? >J v);

$


## i. an" error occurs

eprintStack+race();

$


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$

$

Output

pathname: test.txt

Description

Thejava.io.File.getPath()method converts the abstract pathname into pathname string. To separate the names in the name sequence the

resulting string uses the default name-separator character.

Declaration

Following is the declaration for java.io.File.getPath() method:

public StringgetPath()

Parameters

Not Applicable.

Return Value

The method returns pathname string form of this abstract pathname.

Exception

Not Applicable.

exception handling examples

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