Prerequisites for Java foreach traversal

Self-summary, welcome to shoot bricks, greatly appreciated!

Purpose: To deepen the effect of the foreach traversal

Proof: The foreach traversal is conditional on the list!=null instead of: List!=null && list.size () >0

Description: jdk-version:1.6

 Public Static void Main (string[] args) {        Listnull;     //     list<string> List = new arraylist<string> ();         for (String temp:list) {            System.out.println (temp);        }        System.out.println ("over");}

Phenomenon: When a list is NULL, a null pointer exception is reported when walking to a foreach statement

No exception was reported when List =new arraylist<string>

Summary: list.size () > 0 is not a necessary precondition for foreach, and list! = NULL is the precondition for foreach

Prerequisites for Java foreach traversal