system . out . println(3)；

//The second one is declared first, then assigned, and then output.

int a；

system . out . println(a = 3)；

//The third directly declares assignment and outputs it.

int a 1 = 3；

system . out . println(a 1)；

Data expansion: Java is an object-oriented programming language, which not only absorbs the advantages of C++ language, but also abandons the concepts of multiple inheritance and pointers that are difficult to understand in C++, so Java language has two characteristics: powerful function and simple use. As a representative of static object-oriented programming language, Java language has well realized the object-oriented theory.