javaauto

Is there auto type inferring in Java?

Is there an auto variable type in Java like you have in C++?

An example:

for ( auto var : object_array)
    std::cout << var << std::endl;

for( auto var : object_array)
    var.do_something_that_only_this_particular_obj_can_do();

I know that there is an enhanced for loop in Java, but is there an auto? If not, is there a hack to doing this? I am referring to the new feature in C++11.

Solution

  • Java 10 introduced a var identifier which is like C++ auto; see sorrymissjackson's answer.

    Prior to Java 10, there was no equivalent to the auto keyword. The same loop can be achieved as:

    for ( Object var : object_array)
  System.out.println(var);

    Java has local variables, whose scope is within the block where they have been defined. Similar to C and C++, but there is no auto or register keyword. However, the Java compiler will not allow the usage of a not-explicitly-initialized local variable and will give a compilation error (unlike C and C++ where the compiler will usually only give a warning). Courtesy: Wikipedia.

    There wasn't any mainstream type-inference in Java like C++ . There was an RFE but this was closed as "Will not fix". The given was:

    Humans benefit from the redundancy of the type declaration in two ways. First, the redundant type serves as valuable documentation - readers do not have to search for the declaration of getMap() to find out what type it returns. Second, the redundancy allows the programmer to declare the intended type, and thereby benefit from a cross check performed by the compiler.