Java finally keyword

About the finally statement block, has the following characteristics:

The 1.finally statement block can be directly associated with a try statement block. Try...finally ...

2.try...catch...finally can also

3. The code that is usually in the finally statement block is bound to execute.

See the following example:

import java.io.*;
public class ExceptionTest08{
 public static void main(String[] args){
   try{
     System.out.println("ABC");
     return;
   }finally{
     System.out.println("Test");
   }
 }
}

After compiling the run-time output:

ABC
Test

Typically, return is executed, the method ends, that is, the code after the return is no longer executed. However, since it is followed by a finally statement block, it is said that the finally statement block must be executed, so System.out.println ("Test");

Take a look at the following example:

Import java.io.*;
Public  class   exceptiontest08{
     Public   static   Void   main ( string[) args) throws filenotfoundexception{
      try{
      fileinputstream fis=  new  FileInputStream ( "C:/ab.txt");   //exception occurred 
       //due to an exception in the above code, Therefore System.out.println ("BASIC") will not execute. 
      system.  out.println ( "BASIC"); 
    }  finally{
       //The code in the finally statement block is bound to execute. 
      system.  out.println ( "AAA"); 
    } 
  } 
}            

After compiling the run-time output:

Aaa
ExceptionInchThread"MainJava. io. FileNotFoundException:C +Ab. txt(The system cannot find the file specified.) )
AtJava. io. FileInputStream. Open0 (NativeMethod)
  at   java . io . FileInputStream . Open ( unknown   Source) 
          at&NBSP;  java . io . fileinputstream.<  init> ( unknown&NBSP;  Source) 
          at&NBSP;  java . io . fileinputstream.<  init> ( unknown&NBSP;  Source) 
          at&NBSP;  ExceptionTest08 . Main (  ExceptionTest08 . Java : $)             

There is only one case where the finally statement block is not executed.

import java.io.*;
public class ExceptionTest08{
 public static void main(String[] args){
   try{
     //退出Java虚拟机
     System.exit(0);
   }finally{
     System.out.println("AAA");
   }
 }
}

The above code exits the Java virtual machine in the Try statement block, causing the content in the finally statement block to no longer execute. That is, the contents of the finally statement block are no longer executed as long as the JVM is exited before the finally statement block is executed.

Let's take a closer look at the finally statement block. Take a look at the following example: (Before compiling and running, you can analyze the output of what the result is)

PublicClassexceptiontest09{
PublicStatic   void   Main (  string[] args) {
      int i=m1 (); 
    system.  out.println (i);   
  } 
     public   static   int   M1 () {
      int i=  ten; 
      try{
        return i; 
    }  finally{
      i++; 
      system.  Out.println ( "M1 i=" +i);   
    } 
  } 
}        

After compiling the run-time output:

m1的i=11
10

Take a look at how the above code works:

PublicClassexceptiontest09{
PublicStaticvoidMain string[] args) {
      int i=m1 (); 
    system.  out.println (i);   //10 
   
     Public    static   Int   M1 () {
      int  i=  ten; 
      try{
        int temp=i; 
        return TEMP; 
    }  finally{
      i++; 
      system.  Out.println ( "M1 i=" +i);   //11 
    } 
  } 
}       

Call the M1 () method in the main method, first execute the SYSTEM.OUT.PRINTLN ("M1 i=" +i) in the M1 () method, output M1 i=11, and then execute System.out.println (i) in the main method; Output 10.

Finally statement block also has a role, finally statement block is bound to execute, so usually in the program, in order to ensure that a resource must be released, generally in the finally statement block to release resources.

Importjava.io.*;
PublicClassexceptiontest10{
PublicStatic  void   main  (string[] args) {
     FileInputStream fis=  null; 
   &NBSP  try{
      fis=  new  FileInputStream ( "Exceptiontest10.java"); 
    }  catch (FileNotFoundException e) {
      e.printstacktrace (); 
    }  finally{
       //In order to ensure that resources are bound to be freed, the code block that frees the resource is placed in the finally statement block. 
        if (fis!=  null) {
          try{
       & nbsp  fis.close (); 
        }  catch (IOException e) {
          e.printstacktrace (); 
        } 
      } 
    } 
  ,} 
} 
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Java finally keyword