import java.util.ArrayList; public class RunoobTest { public static void main(String[] args) { ArrayList<String> sites = new ArrayList<String>(); sites.add("Google"); sites.add("Runoob"); sites.add("Taobao"); sites.add("Weibo"); System.out.println(sites.get(1)); // 访问第二个元...
String str = (String) list.get(0); int num = (int) list.get(1); 总结:在ArrayList中添加两种不同的数据类型可以通过使用List或者ArrayList的泛型参数为Object来实现。但是需要注意在取出元素时进行类型转换。 相关搜索: 在具有不同索引和大小的arraylist上添加未重复的元素 在JAVA代码的...
*/ public java.util.Iterator<AnyType> iterator() { return new ArrayListIterator(); } /** * Returns a String representation of this collection. */ public String toString() { StringBuilder sb = new StringBuilder("[ "); for (AnyType x : this) sb.append(x + " "); sb.append("]")...
Collections.sort() 方法对 ArrayList 的元素或者任何其他 List 的实现提供的可比较的元素进行排序,这意味着这些元素的类需要实现 java.lang 包中的 Comparable 接口。正如 String 类实现了 Comparable 接口,我们就可以对由国名构成的 ArrayList 排序。有些其他的标准 Java 类实现了 Comparable 接口,包括原始的包装类,...
public class ArrayListDemo02 {public static void main(String[] args) {//创建集合ArrayList<String> array = new ArrayList<String>();//添加元素array.add("hello");array.add("world");array.add("java");//public boolean remove(Object o):删除指定的元素,返回删除是否成功System.out.println(array....
In the examples above, we created elements (objects) of type "String". Remember that a String in Java is an object (not a primitive type). To use other types, such as int, you must specify an equivalent wrapper class: Integer. For other primitive types, use: Boolean for boolean, ...
This is fast and works for all kinds of lists, but is not entirely flexible (only sequential forward with no deletions, additions, or multiple references). This should be your first choice in programming. Works efficiently with both ArrayList and LinkedList. ArrayList<String> a = new ...
import java.util.List; public class TestDemo01 { public static void main(String[] args) { List list = new ArrayList(); //ArrayList:底层实现时数组,线程不安全,效率高。所以,查询快。修改、插入、删除慢。 //LinkedList:底层实现是链表,线程不安全,效率高。所以,查询慢。修改、插入、删除快。
ArrayList<String>names=newArrayList<String>(){{add("John");add("Alice");}};System.out.println(names);#Output:#[John,Alice] Java Copy 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 ...
safe variant ofArrayListin which all mutative operations (add, set, and so on) are implemented by making a fresh copy of the underlying array. This class is very useful when we cannot or do not want to synchronize the traversals of the arraylist. It is part of thread-safe Java ...