Index overflow in Java for loop

The following little code snippet shows the overflow of for loop index in Java.

public class Out {
    public static void main(String[] ars) {
        for(int i = 0; i <= 2147483647 ; i+=100000000 )
        {
            System.out.println( i + "\n" );
        }        
    }
}

You may expect that the iteration count is 22. But it is not true. i is 2100000000 after the 22nd iteration. Then 100000000 is added to i(2100000000) again. 2200000000 is bigger than 2147483647. So int overflow will happen. i will become a negative integer. So the loop will continue.

For details of loop index overflow, you can refer to Programming Language Pragmatics.

Genenared methods values and valueOf for Enum

I have recently tried Java Enum when doing software development. The following code is an example:

public Enum FooType {
    ABC, DEF;
}

I found two methods valueOf and values in the Javadoc for my enum code. I did not write these 2 methods. And it's superclass java.lang.Enum<FooType> also does not have these 2 methods. Then I checked JLS 3.0. 8.9 Enums says these 2 methods are automatically generated. It is a little magic. One Java class can has methods which do not exist as source code. Too many magic which do not have a consistent rationale can make a language hard to learn and use.