Question

我有这个代码，它工作正常：

News news_data[] = new News[] {
new News("1","news 1","this is news 1"),
new News("2","news 2","this is news 2"),
new News("2","news 1","this is news 2"),
};

在这段代码中我添加了3个新对象，但我必须在循环中动态添加它们。我怎样才能做到这一点？我实际上并不了解这个数组结构。如果你能简单的话，请向我解释一下这段代码

我尝试了这个，但它不起作用：

   News news_data[];
   for(i=1;i<3;i++){
      news_data=new News[] {
          new News("1","news 1","this is news 1"),
          new News("2","news 2","this is news 2"),
          new News("2","news 1","this is news 2"),
      };
   }

Answer 1

Java中没有动态分配，Lists就是出于此目的。例如，List，ArrayList，LinkedList ...

以这种方式使用：

// Declaring, initializing the list
ArrayList<News> list = new ArrayList<News>();
// Adding a news :
News news = new News("1","news 1","this is news 1");
list.add(news);

如果您已经有News数组（在您的示例news_data中），则可以快速填写列表以开始：

for(News n : news_data) { list.add(n); }

Answer 2

使用List。这就是列表的用途：

List<News> news = new ArrayList<News>();
news.add(new News(...));

Answer 3

如果您主要在列表中间添加和删除对象（顺序很重要），最好使用LinkedList。如果经常使用随机访问，则ArrayList是更好的选择，在这种情况下，您可以在O（1）时间内向末尾添加元素。见http://en.wikiversity.org/wiki/Java_Collections_Overview

Answer 4

News news_data[] = new News[3]; // defining the size of Array to 3
new_data[0] = new News("1","news 1","this is news 1"),
new_data[1] = new News("2","news 2","this is news 2"),
new_data[2] = new News("2","news 1","this is news 2"),

但更好的方法是用户ArrayList。它们是为动态结构而制作的。

List<news> news_data = new ArrayList<News>();
news_data.add(new News("1","news 1","this is news 1"));
news_data.add(new News("2","news 2","this is news 2"));
news_data.add(new News("2","news 1","this is news 2"));

动态添加对象到数组

4 个答案: