In Gao Qi's Java video, how can this statement that directly assigns an int type value to an Integer object pass compilation?

Question

I recently read Gao Qi’s Java 300 tutorial, and there was a line of code in it that Teacher Gao briefly mentioned, but upon closer inspection, I felt that I didn’t understand the knowledge points contained in it. The code is as follows:

public class Test063 {
    public static void main(String[] args){
    Integer i = Integer.parseInt("234");
    System.out.println(i);
    }
}

In the second sentence, Interger.parseInt("234"), I checked the source code,

It is clearly stated above that the parseInt method returns a value of type int, but how can it be directly assigned to an Integer object?

I did another experiment

Integer a = 1;//报错
Integer b = Integer.parseInt("1");//编译通过

The result made me very confused. Why is this happening?

Mengxin asks for answers. Thank you!

Answer 1

I am new to you, which version of JDK do you have? I wrote Integer i = 1; on my IDE and it was no problem. I recently updated it to JDK8, but I think JDK7 should also be OK. I don’t know about the previous version. What are the limitations on autoboxing. Why don't you try upgrading?

Answer 2

After JDK 1.5, there is an automatic packaging and automatic unpacking feature, which will automatically convert this primitive data type and its object type. Official document:

https://docs.oracle.com/javas...

Answer 3

After JDK1.5, automatic boxing and unboxing are possible

Answer 4

The teacher’s code is an automatic boxing process, and Integer is the packaging class of int. Your JDK version should be older.