In this example, we create a new anonymous inner class that extends ArrayList. The instance initializer (the block of code inside the double braces) adds ‘John’ and ‘Alice’ to the ArrayList. Advantages and Disadvantages The Stream API and Double Brace Initialization offer more advanced ways ...
/*** Returns {@codetrue} if the iteration has more elements. * (In other words, returns {@codetrue} if {@link#next} would * return an element rather than throwing an exception.) * *@return{@codetrue} if the iteration has more elements*/booleanhasNext();/*** Returns the next eleme...
ArrayList简介 ArrayList是基于数组实现的,是一个动态数组,其容量能自动增长,类似于C语言中的动态申请内存,动态增长内存。 ArrayList不是线程安全的,只能用在单线程环境下,多线程环境下可以考虑用Collections.synchronizedList(List l)函数返回一个线程安全的ArrayList类,也可以使用concurrent并发包下的CopyOnWriteArrayList类。
Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 2, Size: 0 at java.util.ArrayList.rangeCheckForAdd(ArrayList.java:665) at java.util.ArrayList.add(ArrayList.java:477) at org.itstack.interview.test.ApiTest.main(ApiTest.java:13) Process finished with exit code 1 🤭谢...
{ modCount++; // overflow-conscious code if (minCapacity - elementData.length > 0) grow(minCapacity); } private void grow(int minCapacity) { // overflow-conscious code int oldCapacity = elementData.length; // 扩展为原来的1.5倍 int newCapacity = oldCapacity + (oldCapacity >> 1); // ...
在 getSortedJobCandidateByName()方法内部,我们又调用了 Collections.sort()的另一个重载版本,这个版本传递要被排序的 ArrayList 对象和比较姓名的 Comparator 对象。 Let’s write a test class to test our code. 让我们写一个测试类来测试我们的代码。JobCandidateSorterTest.java...
contains()方法调用了indexOf()方法,indexOf()具体实现如下。从源码可以看出,该方法通过遍历数据和比较元素的方式来判断是否存在给定元素。当ArrayList中存放的元素非常多时,这种实现方式来判断效率将非常低,后面通过实例来验证。 1.2 HashSet 既然ArrayList的contains()方法存在性能问题,那么就应该寻找改进的办法。这里推...
In this quick article, we had a look at the ArrayList in Java. We showed how to create anArrayListinstance, how to add, find or remove elements using different approaches. As usual, you can find all the code samplesover on GitHub.
// overflow-conscious code if (minCapacity - elementData.length > 0) grow(minCapacity); } 1. 2. 3. 4. 5. 6. 7. 3.6 set方法 set 方法的作用是把下标为 index 的元素替换成 element,同时返回替换之前的旧值。 同get方法十分类似,在替换元素之前,也是先通过 rangeCheck 方法判断一下下标index是否...
* @param c collection containing elements to be retained in this list * @return {@code true} if this list changed as a result of the call * @throws ClassCastException if the class of an element of this list * is incompatible with the specified collection ...