关于计算机科学入门测验的问题

Question

I recently came across this question on the Saylor Academy intro to CS quiz. It's about the syntax in Java. Could someone please explain what I'm missing?

Compiler says I am correct.

Answer 1

That is a blatant mistake on their part. I do not think any Java version accepts this code - ie, this is a compilation error and your answer is correct. You can run it anywhere to verify this:

>cat test.java
public class test {
    public static void main(String[] argv) {
        int x+= 1;
    }
}
>java test.java
test.java:3: error: ';' expected
        int x+= 1;
             ^
1 error
error: compilation failed

Answer 2

Its true when the value of x is set during variable declaration the expression above will not result into an error the code below explains it better

public class HelloWorld{

     public static void main(String []args){
        int x = 5;
        x  += 1;
        System.out.println(x);
        //the value of x would be six ie original value of x plus 1
     }
}