Is there auto type inferring in Java? Is there auto type inferring in Java? java java

Is there auto type inferring in Java?


Might be Java 10 has what you (and I) want, through the var keyword.

var list = new ArrayList<String>();  // infers ArrayList<String>var stream = list.stream();          // infers Stream<String>

From JDK Enhancement Proposals 286


Update: Yap, that feature made it into the Java 10 release!


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 nothave to search for the declaration of getMap() to find out what type itreturns. Second, the redundancy allows the programmer to declare the intendedtype, and thereby benefit from a cross check performed by the compiler.


Java 7 introduces the diamond syntax

Box<Integer> integerBox = new Box<>(); // Java 7

As compared to old java

Box<Integer> integerBox = new Box<Integer>(); // Before Java 7

The critical reader will notice that this new syntax doesn't help with writing the for loops in the original question. That's correct and fully intentional it seems. See the other answer that cites Oracle's bug database.