Java中的ArrayList类是List接口的Resizable-array实现。它允许空值。
此类的clear()方法从当前List对象中删除所有元素。
import java.util.ArrayList; public class ClearExample { public static void main(String[] args){ //Instantiating an ArrayList object ArrayList<String> list = new ArrayList<String>(); list.add("JavaFX"); list.add("Java"); list.add("WebGL"); list.add("OpenCV"); list.add("Impala"); System.out.println("Contents of the Array List: \n"+list); //Removing the sub list list.clear(); System.out.println("Contents of the ArrayList object after invoking the clear() method: "+list); } }
输出结果
Contents of the Array List: [JavaFX, Java, WebGL, OpenCV, Impala] Contents of the ArrayList object after invoking the clear() method: []
而ArrayList类的removeAll()方法接受另一个集合对象作为参数,并从当前ArrayList中删除其所有内容。
import java.util.ArrayList; public class ClearExample { public static void main(String[] args){ //Instantiating an ArrayList object ArrayList<String> list1 = new ArrayList<String>(); list1.add("JavaFX"); list1.add("Java"); list1.add("WebGL"); list1.add("OpenCV"); list1.add("OpenNLP"); list1.add("JOGL"); list1.add("Hadoop"); list1.add("HBase"); list1.add("Flume"); list1.add("Mahout"); list1.add("Impala"); System.out.println("Contents of the Array List1 : \n"+list1); ArrayList<String> list2 = new ArrayList<String>(); list2.add("JOGL"); list2.add("Hadoop"); list2.add("HBase"); list2.add("Flume"); list2.add("Mahout"); list2.add("Impala"); System.out.println("Contents of the Array List1 : \n"+list2); //Removing elements list1.removeAll(list2); System.out.println("Contents of the Array List after removal: \n"+list1); } }
输出结果
Contents of the Array List1 : [JavaFX, Java, WebGL, OpenCV, OpenNLP, JOGL, Hadoop, HBase, Flume, Mahout, Impala] Contents of the Array List1 : [JOGL, Hadoop, HBase, Flume, Mahout, Impala] Contents of the Array List after removal: [JavaFX, Java, WebGL, OpenCV, OpenNLP]