如何用 Java 将集合中的所有项添加到数组列表中？
原文:https://www . geesforgeks . org/如何将集合中的所有项目添加到 java 中的数组列表/
给定一个带有一些值的集合，任务是将该集合的所有项目添加到 Java 中的数组列表中。
插图:
Input: Collection = [1, 2, 3]
Output: ArrayList = [1, 2, 3]
Input: Collection = [GFG, Geek, GeeksForGeeks]
Output: ArrayList = [GFG, Geek, GeeksForGeeks]
进场:
- 获取要将其项添加到数组列表中的集合
- 创建数组列表
- 使用 ArrayList.addAll()方法将集合的所有项目添加到该 ArrayList 中
- 已创建包含所有集合项的数组列表。
例
Java 语言(一种计算机语言，尤用于创建网站)
// Java Program to Add All Items from a collection
// to an ArrayList
// Importing required classes
import java.io.*;
import java.util.*;
import java.util.stream.*;
// Main class
class GFG {
// Method 1
// To add all items from a collection
// to an ArrayList
public static <T> ArrayList<T>
createArrayList(List<T> collection)
{
// Creating an ArrayList
ArrayList<T> list = new ArrayList<T>();
// Adding all the items of Collection
// into this ArrayList
list.addAll(collection);
return list;
}
// Method 2
// Main driver method
public static void main(String[] args)
{
// Getting array elements as list
// and storing in a List object
List<Integer> collection1 = Arrays.asList(1, 2, 3);
// Printing elements in above List object
System.out.println("ArrayList with all "
+ "elements of collection "
+ collection1 + ": "
+ createArrayList(collection1));
// Again creating another List class object
List<String> collection2 = Arrays.asList(
"GFG", "Geeks", "GeeksForGeeks");
// Printing elements in above List object
System.out.println("ArrayList with all"
+ " elements of collection "
+ collection2 + ": "
+ createArrayList(collection2));
}
}
Output
ArrayList with all elements of collection [1, 2, 3]: [1, 2, 3]
ArrayList with all elements of collection [GFG, Geeks, GeeksForGeeks]: [GFG, Geeks, GeeksForGeeks]
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