In Java, what exactly constitutes as "initializing a local variable"? -


says that I have a piece of code in the local method 

  int a = 5, b;   
 and then start some code indirectly, such as  
  if (true) b = 5; // legal if (someBool) b = 10; And b = 7; // Legal if (false) B = 5; // Invalid   
 Invalid though B will always be started  
  if (a & gt; 10) b = 4; If (a & lt; = 10) b = 4;   
 My question is whether a local variable can be legally considered "start" in all precise conditions?  
 
 
 
 can be considered to be a local variable "if the compiler can easily assume that every Possible code path will lead through a path where the price has been set. "  
     
  •   Always (always)  can always be set to run.  
  •   If (wrong)  can not be run at any time  
  •   to run at least one branch if / or , you have to assign the variable to each branch if you want it to start.  if / else if /.../ else   
  •  The  switch  statement will probably suppress the  case  s, or  default , so if you specify the variable in all these places May include, is guaranteed to be launched.   
     The Java compiler does not bother checking all the possible values ​​of each variable at different points in the method when determining this, because those variables  variable  - they change However, if the value can be assumed as  stable , then it can safely assume that they will not make changes.  
     For example, the compiler does not care if you specify a variable and never change it in your code:  
      Bully Val = true; If (val) {b = 5; }   
     With the help of debuggers and things you have chosen to change the value of the  value  on-the-fly, so that any compiler assumptions are not here . However, if you are doing tax  val   continuously , with the declared  last  and a continuous or literal value, it is actually compiler Will behave the same as you use the value in the code.  
      last boolean val = true; If (val) {// as if you had said that if (true) `B = 5; }   
     Such constants can be chained, as well, and the compiler will now have to simplify them for their continued values ​​rather than maintaining the expressions and operators:  
      last int five = 5; Last four four = five - 1; // equals `4 = 5 - 1`, or 'four = 4' is the last boolean value = 5 & gt; Four; If (wal) {// `(5> 4) equals` `, or` (if true) `b = 5; }   
     To read more, check out. (Radioop the hat tip to find the right section.)

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