标签：pre family res imp list javac string foreach nbsp
加强的for循环有两种，遍历数组和实现了Iterable接口的容器。javac通过visitForeachLoop()方法来实现解语法糖，代码如下：
/** Translate away the foreach loop. */
public void visitForeachLoop(JCEnhancedForLoop tree) {
if (types.elemtype(tree.expr.type) == null)
visitIterableForeachLoop(tree);
else
visitArrayForeachLoop(tree);
}
首先来看遍历数组。
A statement of the form
for ( T v : arrayexpr )
stmt;
(where arrayexpr is of an array type) gets translated to
for ( { arraytype #arr = arrayexpr;
int #len = array.length;
int #i = 0; };
#i < #len; i$++ ) {
T v = arr$[#i];
stmt;
}
where #arr, #len, and #i are freshly named synthetic local variables.
举个例子，如下：
Integer[] array = { 1, 2, 3, 4, 5 };
for (Integer i : array) {
System.out.println(i);
}
解语法糖后的结果如下：
for (Integer[] arr$ = array, len$ = arr$.length, i$ = 0; i$ < len$; ++i$) {
Integer i = arr$[i$];
{
System.out.println(i);
}
}
来看看对容器的遍历，如下：
A statement of the form
for ( T v : coll )
stmt ;
(where coll implements Iterable<? extends T>) gets translated to
for ( Iterator<? extends T> #i = coll.iterator(); #i.hasNext(); ) {
T v = (T) #i.next();
stmt;
}
where #i is a freshly named synthetic local variable.
List<String> list = new ArrayList<String>();
for(String str:list){
System.out.println(str);
}
解语法糖后的结果如下：
for (java.util.Iterator i$ = list.iterator(); i$.hasNext(); ) {
String str = (String)i$.next();
{
System.out.println(str);
}
}
标签：pre family res imp list javac string foreach nbsp
原文地址：http://www.cnblogs.com/extjs4/p/7396813.html
