importjava.util.ArrayList;importjava.util.Iterator;importjava.util.List;publicclassMain{publicstaticvoidmain(String[]args){List<Integer>list=newArrayList<>();list.add(1);list.add(2);list.add(3);list.add(4);List<Integer>newList=newArrayList<>();Iterator<Integer>iterator=list.iterator();while(...
通过调用集合类的iterator()方法可以获得一个Iterator对象,然后使用while循环和next()方法来遍历集合中的元素,如下所示: List<String>list=newArrayList<>();list.add("Java");list.add("Android");list.add("Kotlin");Iterator<String>iterator=list.iterator();while(iterator.hasNext()){Stringitem=iterator.nex...
Java的Iterable类也对for each 循环有很大作用(就下面这种` for(ElementTypevariable:collection){loopBody// may refer to "variable"} 所有实现iterable的collections都支持这种循环操作,本质上说上面的代码就是下面代码的简化版: Iterator<E>iter=collection.iterator();while(iter.hasNext()){Evariable=iter.next(...
Classic for loop 首先,来看看classic for loop. List<String> birds =new ArrayList<String>() { { add("magpie"); add("crow"); add("emu"); } }; for (int i =0; i < birds.size(); i++) { String bird = birds.get(i); } 这种方式,代码风格还好,可惜的是,有个隐藏的性能问题。 对...
Java对迭代提供很多支持: (1)For,while和repeat循环,通常使用整数的索引; (2)Enumeration类(在java.util中); (3)Iterator类(也存在于java.util中),支持JDK1.2中的集合; (4)JDK 1.5中增加的对循环的扩展(foreach). 我们将使用Iterator类作为本章介绍重点,本部分主要关注扩展的for循环. ...
cars.add("Mazda");//Get the iteratorIterator<String> it =cars.iterator();//Loop through a collectionwhile(it.hasNext()) { System.out.println(it.next()); } } }//Outputs:Volvo BMW Ford Mazda Removing Items from a Collection importjava.util.ArrayList;importjava.util.Iterator;publicclassMain...
Classic for loop ⾸先，来看看classic for loop.List<String> birds = new ArrayList<String>() { { add("magpie");add("crow");add("emu");} };for (int i = 0; i < birds.size(); i++) { String bird = birds.get(i);} 这种⽅式，代码风格还好，可惜的是，有个隐藏的性能问题。对...
out.println(i); } } // Java 会自动编译成如下代码 private static final void loop() { List<Integer> list = Arrays.asList(1, 2, 3, 4); Iterator var1 = list.iterator(); while(var1.hasNext()) { Integer i = (Integer)var1.next(); System.out.println(i); } } //传入...
Iterators are designed to easily change the collections that they loop through. The remove() method can remove items from a collection while looping.Example Use an iterator to remove numbers less than 10 from a collection: import java.util.ArrayList; import java.util.Iterator; public class Main...
4. Java ListIterator for Bi-directional Iteration on Lists ListIteratorcan be used to iterate in forward as well as backward directions over the elements of anyList-implemented collection classes. UsingListIteratorwe can perform read, remove, add, and update operations while iterating over the ele...