使用for-each循环的三种情况

1.Collection容器类

　　如ArrayList类中

List<String> list = new ArrayList<String>();
    list.add("Red");
    list.add("Yellow");
    list.add("Blue");
    for(String element : list){
        System.out.printf("%s", element);
    }

2.对Arrays数组的遍历

int[] numArray = {1, 2, 3, 4, 5, 6};
for(int count = 0; count<numArray.length; count++){
    System.out.print(numArray[count]);
}
//for-each
for(int element : numArray){
    System.out.print(element);
}

3.实现了接口java.lang.Iterable<T>自行撰写的普通类

public void displayCatalog(){
    if(this.catalog.getNumberOfItems() == 0){
        stdErr.println("The catalog is empty");
    }else{
    for(CatalogItem item : this.catalog){
        stdOut.println(item.getCode() + " " + item.getTitle() + " "
                             + (item.isAvailable() ? "(A)" : "(NA)"));
    }
}//从而Catalog类的实例可以放在：右边