解决方案
以下示例展示了如何通过使用 collection.add() 添加新数据和 collection.size() 获取 Collections 类的集合大小来获取集合的大小。
import java.util.*;
public class CollectionTest {
public static void main(String [] args) {
System.out.println( "Collection Example!\n" );
int size;
HashSet <String>collection = new HashSet <String>();
String str1 = "Yellow", str2 = "White", str3 = "Green", str4 = "Blue";
Iterator iterator;
collection.add(str1);
collection.add(str2);
collection.add(str3);
collection.add(str4);
System.out.print("Collection data: ");
iterator = collection.iterator();
while (iterator.hasNext()){
System.out.print(iterator.next() + " ");
}
System.out.println();
size = collection.size();
if (collection.isEmpty()){
System.out.println("Collection is empty");
} else {
System.out.println( "Collection size: " + size);
}
System.out.println();
}
}
