使用 finally 块捕获异常的Java程序

Java中的finally块用于放置重要的代码，例如清理代码，例如关闭文件或关闭连接。 finally 块会执行异常是否出现以及异常是否被处理。无论异常是否发生，finally 都包含所有关键语句。

有 3 种可能的情况可以使用 finally 块：

案例1：当异常没有上升时

在这种情况下，程序运行良好，不会抛出任何异常，并在 try 块之后 finally 块执行。

Java

// Java program to demonstrate
// finally block in java When
// exception does not rise 
  
import java.io.*;
  
class GFG {
    public static void main(String[] args)
    {
        try {
            System.out.println("inside try block");
            
            // Not throw any exception
            System.out.println(34 / 2);
        }
        
        // Not execute in this case
        catch (ArithmeticException e) {
            
            System.out.println("Arithmetic Exception");
            
        }
        // Always execute
        finally {
            
            System.out.println(
                "finally : i execute always.");
            
        }
    }
}

输出

inside try block
17
finally : i execute always.

情况二：当异常上升并被catch块处理时

在这种情况下，程序抛出异常但由 catch 块处理，并且 finally 块在 catch 块之后执行。

Java

// Java program to demonstrate finally block in java
// When exception rise and handled by catch
  
import java.io.*;
  
class GFG {
    
    public static void main(String[] args)
    {
        try {
            System.out.println("inside try block");
  
            // Throw an Arithmetic exception
            System.out.println(34 / 0);
        }
  
        // catch an Arithmetic exception
        catch (ArithmeticException e) {
  
            System.out.println(
                "catch : exception handled.");
        }
  
        // Always execute
        finally {  
            
          System.out.println("finally : i execute always.");
        }
    }
}

输出

inside try block
catch : exception handled.
finally : i execute always.

情况 3：当异常上升且未被 catch 块处理时 

在这种情况下，程序抛出异常但没有被catch处理，所以finally块在try块之后执行，finally块执行后程序异常终止，但finally块执行正常。

Java

// Java program to demonstrate finally block 
// When exception rise and not handled by catch
  
import java.io.*;
  
class GFG {
    public static void main(String[] args)
    {
        try {
            System.out.println("Inside try block");
  
            // Throw an Arithmetic exception
            System.out.println(34 / 0);
        }
  
        // Can not accept Arithmetic type exception
        // Only accept Null Pointer type Exception
        catch (NullPointerException e) {
  
            System.out.println(
                "catch : exception not handled.");
        }
  
        // Always execute
        finally {
  
            System.out.println(
                "finally : i will execute always.");
        }
        // This will not execute
        System.out.println("i want to run");
    }
}

输出

Inside try block
finally : i will execute always.
Exception in thread "main" java.lang.ArithmeticException: / by zero
    at GFG.main(File.java:10)