A local variable defined with var must be initialized with its declaration, or the code won't compile. The compiler can't infer the type of an uninitialized variable or a variable that is assigned a null value. The following code won't compile:
var minAge; // uninitialized variable var age = null; // variable assigned a null value
The following image illustrates what would happen if the uninitialized variable age went to seek entrance to the Mr. Java compiler place. The compiler won't let age in:
Variable definition using var must always be accompanied by its initialization, or the code will fail to compile.