Anti-compilation See Java For-each loop

The For-each loop introduced in the Java 1.5 release. (from "effective Java" Chinese version of the second edition of the 46th article )

Example of the For-each loop for the following array list:

1  Public classForEach {2      Public Static voidMain (string[] args) {3java.util.arraylist<string> list =NewJava.util.arraylist<string>();4          for(String s:list) {5             //TODO6         }7 }//main8}

In the jdk1.8.0_151 environment, use the Javac tool to compile the code above, get the Foreach.class bytecode file, and then use JAVAP to decompile the bytecode file, as shown in:

Note that the Java.util.Iterator class appears for the anti-compilation result, and its hasnext and next methods appear.

See here, probably also understand, For-each loop in essence is actually the use of the iterator pattern.

To put it simply, the code at the beginning of the article is actually like this:

1  Public classForEach {2      Public Static voidMain (string[] args) {3java.util.arraylist<string> list =NewJava.util.arraylist<string>();4Java.util.iterator<string> iter =list.iterator ();5          while(Iter.hasnext ()) {6 Iter.next ();7         }8}//Main9}

Two comparisons, For-each more concise, this is the advantage of For-each.

Therefore, it can be said that the For-each loop is a syntactic sugar in Java.

"Summary": The For-each loop is Java syntax sugar, which is essentially the use of an iterator pattern.

Anti-compilation See Java For-each loop