The effect of final modifier parameters in Java

The final keyword before the method parameter is to prevent the data from being modified in the method body.

There are two main cases: first, the basic data type is decorated with final, and second, the reference type is decorated with final.

In the first case, the modifier base type (non-reference type). At this point the value of the parameter cannot be modified in the body of the method, i.e. it cannot be re-assigned. Otherwise the compilation will not pass. For example:

1 public static void valid (final int ag) {2         ag=9;3         ag=10;4}

Error message:


In the second case, the reference type is modified. In this case, the object referenced by the parameter variable cannot be changed. As a copy of the reference, the parameter cannot reference the new object in the method body. Otherwise the compilation does not pass. For example:

1 public static void valid (final string[] ag) {2         ag=new string[9];3}

The hints are the same as above. : "The final local variable param2 cannot be assigned. It must is blank and not using a compound assignment. "

But for references, if I were, I wouldn't have reported anything wrong, I could have compiled it all through.

1 public static void valid (final string[] ag) {2         ag[0]= "5"; 3         System.out.println (AG); 4}

So, the final keyword, if you want to use the basic type, or very useful. Reference type, or forget it.

The effect of final modifier parameters in Java