您可以在Java中建立自己的異常，它們被稱為使用者自訂異常或自訂異常。
要建立使用者自訂異常，請擴充上述類別之一。若要顯示訊息，請重寫toString()方法或透過以字串格式繞過訊息呼叫超類別參數化建構子。
MyException(String msg){
super(msg);
}
Or,
public String toString(){
return " MyException [Message of your exception]";
}然後，在其他需要引發此例外的類別中，建立一個已建立的自訂例外類別的對象，並使用throw關鍵字拋出異常。
MyException ex = new MyException ();
If(condition……….){
throw ex;
}#所有例外都必須是Throwable的子類別。
如果您想要寫一個由Handle或Declare規則自動強制執行的已檢查異常，您需要擴充Exception類別。
如果您想寫一個運行時異常，您需要擴充RuntimeException類別。
以下Java程式示範如何建立一個自訂已檢查異常。
線上示範
import java.util.Scanner;
class NotProperNameException extends Exception {
NotProperNameException(String msg){
super(msg);
}
}
public class CustomCheckedException {
private String name;
private int age;
public static boolean containsAlphabet(String name) {
for (int i = 0; i < name.length(); i++) {
char ch = name.charAt(i);
if (!(ch >= 'a' && ch <= 'z')) {
return false;
}
}
return true;
}
public CustomCheckedException(String name, int age){
if(!containsAlphabet(name)&&name!=null) {
String msg = "Improper name (Should contain only characters between a to z (all small))";
NotProperNameException exName = new NotProperNameException(msg);
throw exName;
}
this.name = name;
this.age = age;
}
public void display(){
System.out.println("Name of the Student: "+this.name );
System.out.println("Age of the Student: "+this.age );
}
public static void main(String args[]) {
Scanner sc= new Scanner(System.in);
System.out.println("Enter the name of the person: ");
String name = sc.next();
System.out.println("Enter the age of the person: ");
int age = sc.nextInt();
CustomCheckedException obj = new CustomCheckedException(name, age);
obj.display();
}
}編譯時，上述程式會產生以下例外。
CustomCheckedException.java:24: error: unreported exception NotProperNameException; must be caught or declared to be thrown throw exName; ^ 1 error
如果您只是將自訂例外繼承的類別變更為RuntimeException，它將在執行時間拋出
class NotProperNameException extends RuntimeException {
NotProperNameException(String msg){
super(msg);
}
}如果您執行上述程序，將NotProperNameException類別替換為上面的程式碼並執行它，將產生下列執行時間例外。
Enter the name of the person: Krishna1234 Enter the age of the person: 20 Exception in thread "main" july_set3.NotProperNameException: Improper name (Should contain only characters between a to z (all small)) at july_set3.CustomCheckedException.<init>(CustomCheckedException.java:25) at july_set3.CustomCheckedException.main(CustomCheckedException.java:41)
以上是在Java中的自訂異常的詳細內容。更多資訊請關注PHP中文網其他相關文章！
