Java 中的異常類型

以下文章概述了 Java 中的異常類型。 Java異常在程式執行時扮演著非常關鍵的角色。一般來說，任何程式在執行時異常終止或中斷都會導致異常。 Java Exception 是在創建物件的時候出現的異常，或是執行時間產生的錯誤，異常都與java中的物件有關，因為java是物件導向的程式語言。因此，存在一個異常和錯誤的層次結構，其中包含 throwable、try 和 catch 區塊來捕獲和識別引起的異常。

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Java 中不同類型的異常

Java 程式中負責異常類型的物件建立遵循層次結構，如下所示：

java 程式設計時的異常基本上分為兩類，例如：

• 內建異常：這些是可以使用現有的 java 庫捕獲的異常類型。它也稱為未檢查異常或運行時異常。
• 使用者定義的異常：這些異常類型可以使用使用者建立的一些自訂異常來捕獲，並且使用者應該有能力處理這些異常。這些異常也可以稱為檢查異常或編譯時異常。

1.內建異常的類型

• 算術異常
• ClassNotFoundException
• IOException
• ArrayIndexOutOfBoundsException
• FileNotFoundException
• 空指標異常
• NoSuchFieldException
• NoSuchMethodException
• StringIndexOutOfBoundsException
• 運行時異常
• NumberFormatException
• 中斷異常

a.算術異常

每當算術計算時出現一些不符合時，就會呼叫此異常。

範例：

該程式示範了算術異常。

代碼：

public class Arithmtic_excpn {
public static void main(String[] args) {
{
try {
int first_no = 0;
int scnd_no = 20;
int third_no = 0;
int fourth_no = (first_no-scnd_no)/third_no;
System.out.println ("output after the operation " + fourth_no );
}
catch(ArithmeticException arithmetic_ex) {
System.out.println ("The third number cannot store the value of first number multiplied by second number.");
}
}
}
}

輸出：

b. ClassNotFoundException

如果任何類別未正確定義，則會導致 ClassNotFoundException。

範例：

程式示範了 ClassNotFoundException。

代碼：

public class Not_Found_Excp {
private static final String mysql_connector = "com.jdbc.mysql-connector";
public static void main(String[] args) throws Exception {
System.out.println("search for the mysql-connector of jdbc for establishing connection.");
Class.forName(mysql_connector);
}
}

輸出：

c. IO異常

當任何一個輸入或輸出異常終止且操作失敗時，就會導致 IO 異常。

範例：

該程式演示了 IO 異常。

代碼：

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
public class IO_Excption_Ex {
public FileInputStream testMethod1(){
File file_a = new File("123.txt");
FileInputStream fileInptstrm = null;
try{
fileInptstrm = new FileInputStream(file_a);
fileInptstrm.read();
}catch (IOException excpn){
excpn.printStackTrace();
}
finally{
try{
if (fileInptstrm != null){
fileInptstrm.close();
}
}catch (IOException excpn){
excpn.printStackTrace();
}
}
return fileInptstrm;
}
public static void main(String[] args){
IO_Excption_Ex inst_1 = new IO_Excption_Ex();
inst_1.testMethod1();
}
}

輸出：

d. ArrayIndexOutOfBoundsException

每當索引存取錯誤，且索引的範圍不可達，無法存取時，就會出現ArrayIndexOutOfBoundsException

範例：

程式示範了 ArrayIndexOutOfBoundsException。

代碼：

public class Arr_Indx_Out_Of_BOnd {
public static void main(String[] args) {
try{
int ar_0[] = new int[6];
ar_0[8] = 11;
}
catch(ArrayIndexOutOfBoundsException excp){
System.out.println ("Index of the array has crossed the range.");
}
}
}

輸出：

e.文件找不到異常

如果任何檔案在路徑中未正確提及或未正確打開，則會拋出 FileNotFoundException

範例：

此程式示範了 FileNotFoundException。

代碼：

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
public class File_Not_Found_Excpt_Exmpl {
private static final String file_nm = "jkl.txt";
public static void main(String[] args) {
BufferedReader rder = null;
try {
rder = new BufferedReader(new FileReader(new File(file_nm)));
String inpt_ln = null;
while ((inpt_ln = rder.readLine()) != null)
System.out.println(inpt_ln);
} catch (IOException excpn) {
System.err.println("catch the IO Exception.");
excpn.printStackTrace();
} finally {
try {
rder.close();
} catch (IOException excpn) {
System.err.println("catch the IO Exception.");
excpn.printStackTrace();
}
}
}
}

輸出：

f.空指標異常

只要物件的成員指向或引用任何空值，就會發生這種類型的異常。

範例：

該程式演示了空指標異常。

代碼：

public class Null_Pointer_Excp {
public static void main(String[] args) {
try {
String art_1 = null;
String art_3= "abc";
System.out.println(art_1.charAt(0));
} catch(NullPointerException excpn) {
System.out.println("This will give a null pointer exception.");
}
}
}

輸出：

g。 NoSuchFieldException

只要不存在欄位或存在任何變量，就會發生此異常。

範例：

此程式示範了 NoSuchFieldException。

代碼：

import java.text.DateFormat.Field;
import java.lang.reflect.*;
public class No_suc_field_excpn_Ex {
public static void main(String[] args) {
No_suc_field_excpn_Ex excp = new No_suc_field_excpn_Ex();
Class any_cls = excp.getClass();
System.out.println("value_of_field=");
try {
java.lang.reflect.Field strng_fld = any_cls.getField("One_strng");
System.out.println("field for the public superclass is found: " + strng_fld.toString());
} catch(NoSuchFieldException excpn) {
System.out.println(excpn.toString());
}
}
public No_suc_field_excpn_Ex() {
}
public No_suc_field_excpn_Ex(String One_strng) {
this.val_OneStrng = One_strng;
}
public String val_OneStrng = "Everything appears to be Exception.";
}

輸出：

h. NoSuchMethodException

While trying to access any method in a class and that method is not defined clearly or else is missing will lead to NoSuchMethodException.

Example:

This program demonstrates the NoSuchMethodException.

Code:

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
public class No_Sch_mthd_Ex {
public static String add_rss;
public static String somefiletext;
public static String initial_page_src;
public static void Calculate() throws MalformedURLException {
URL url_a = new URL(add_rss) ;
URLConnection connect_2 = null;
try {
connect_2 = url_a.openConnection();
} catch (IOException excp) {
excp.printStackTrace();
}
BufferedReader buffrr = null;
try {
buffrr = new BufferedReader(
new InputStreamReader(connect_2.getInputStream()));
} catch (IOException excpn) {
excpn.printStackTrace();
}
String filnm_z = "C:\\Users\\adutta\\Documents\\"+"page_src"+"123.txt";
File file_o = new File(filnm_z);
if (!file_o.exists()) {
try {
file_o.createNewFile();
} catch (IOException excpn) {
excpn.printStackTrace();
}
}
FileWriter flwrtr = null;
try {
flwrtr = new FileWriter(filnm_z);
} catch (IOException exc) {
exc.printStackTrace();
}
BufferedWriter bw = new BufferedWriter(flwrtr);
String textreader;
try {
while ((textreader = buffrr.readLine()) != null) {
bw.write(textreader);
}
} catch (IOException excn) {
excn.printStackTrace();
}
}
public static void set_page_src(String page_src){
page_src = initial_page_src;
}
public static void set_url(String addressname){
addressname = add_rss;
}
public static void set_text_file_name(String celeb_filename_p){
celeb_filename_p = celeb_name_i;
}
public static String celeb_name_i = "type_the_text" ;
public static  String url_add_ress = "http//ooo.com";
public static void main(String[] args) {
No_Sch_mthd_Ex.set_page_src(celeb_name_i);
No_Sch_mthd_Ex.set_url(url_add_ress);
try {
No_Sch_mthd_Ex.Calculate();
} catch (IOException excpn) {
excpn.printStackTrace();
}
}
}

Output:

i. StringIndexOutOfBoundsException

If the index ranging is negative or more than the defined index range in the string class, then it will result into this exception of StringIndexOutOfBoundsException.

Example:

This program demonstrates the StringIndexOutOfBoundsException.

Code:

public class String_Inx_Out_Of_Bound_Ex {
public static void main(String[] args) {
try {
String ant = "ant crawls very slowly.";
char chrct = ant.charAt(50);
System.out.println(chrct);
}
catch(StringIndexOutOfBoundsException excepn) {
System.out.println("String_Out_Of_Bound_Exception occured.");
}
}
}

Output:

j. RuntimeException

During runtime if any kind of exception arise then these types of exceptions are known as RuntimeException.

Example:

This program demonstrates the RuntimeException.

Code:

public class Runtime_Excp_Ex {
public void Demo_Runtime_Exception () {
throw new Running_Exception();
}
public static void main(String[] args) {
try {
new Running_Exception().Demo_Runtime_Exception();
} catch(Exception excpn) {
System.out.println(excpn.getClass().getName());
}
}
}
class Running_Exception extends RuntimeException {
public Running_Exception() {
super();
}
public void Demo_Runtime_Exception() {
throw new Running_Exception();
}
}

Output:

k. NumberFormatException

Any exception which cannot get converted into numeric format from the string defined then it will lead to NumberFormatException.

Example:

This program demonstrates the NumberFormatException.

Code:

public class No_Format_Ex {
public static void main(String[] args) {
try {
int value1 = Integer.parseInt ("parasite1") ;
System.out.println(value1);
} catch(NumberFormatException excepn) {
System.out.println("This gives Number Format Exception");
}
}
}

Output:

l. InterruptedException

If a thread gets disturbed at the time of waiting, sleeping or while performing some processing then it leads to interrupted Exception.

Example:

This program demonstrates the InterruptedException.

Code:

class ChildThread extends Thread {
public void run() {
try {
Thread.sleep(500);
} catch (InterruptedException excpn) {
System.err.println("Interuppted_Exception occured.");
excpn.printStackTrace();
}
}
}
public class Interuupted_Excpt_Exmple {
public static void main(String[] args) throws InterruptedException {
ChildThread chldth1 = new ChildThread();
chldth1.start();
chldth1.interrupt();
}
}

Output:

2. User-Defined Exception

This exception occurs whenever there is some customizable or errors done by user while implementation and execution of program.

Example:

This program demonstrates the user-Defined Exception.

Code:

public class My_Excpn extends Exception {
private static int roll_no[] = {10, 15, 23, 30};
private static String student_Nm[] = {"ani", "viky", "nidhi", "ash"};
private static double marks[] = {20.5, 44.6, 30, 17};
My_Excpn() {    }
My_Excpn(String str)
{
super(str);
}
public static void main(String[] args) {
try  {
System.out.println("roll_no" + "\t" + "student_Nm" +
"\t" + "marks");
for (int i = 0; i < 4 ; i++)
{
System.out.println(roll_no[i] + "\t" + student_Nm[i] +
"\t" + marks[i]);
if (marks[i] < 60)
{
My_Excpn mrk1 =
new My_Excpn("Student will fail if marks is less than 60");
throw mrk1;
}
}
}
catch (My_Excpn excpn) {
excpn.printStackTrace();
}
}
}

Output:

Conclusion

Exceptions in java plays a very pivotal role because it helps in catching and simultaneously throwing of the root cause for an abnormal termination of the program. It often causes and consumes a lot of time for programmers to run and execute programs therefore these kinds of fatal exceptions should not occur frequently at the time of production or even implementation.

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