在java中添加數組列表

Question

是否可以連接兩個或更多數組列表？我有以下情況：

private Arraylist<Double> getContextVectorsize(int sizeContext){ 
    ArrayList<Double> contextList = new ArrayList<Double>(); 
    for(int i =0 ; i< sizeContext; i++){ 
     contextList = //TODO 
    } 
} 

我想追加所有的ArrayList爲了和希望產生的 size = sizeContext*ArraylistOfSingleMember

Answer 1

你可以使用則addAll（）方法的ArrayList。

Answer 2

for(int i =0 ; i< sizeContext; i++){ 
    contextList.addAll(an instance of ArrayList<Double>); 
} 

Answer 3

使用list1.addAll（列表2），如果它的工作和更新列表1返回true。以下是來自tutorialspoint.com的完整代碼示例。

import java.util.ArrayList; 

public class ArrayListDemo { 
    public static void main(String args[]) { 

    // create an empty array list1 with an initial capacity 
    ArrayList<Integer> arrlist = new ArrayList<Integer>(5); 

    // use add() method to add elements in the list 
    arrlist.add(12); 
    arrlist.add(20); 
    arrlist.add(45); 

    // let us print all the elements available in list1 
    System.out.println("Printing list1:"); 
    for (Integer number : arrlist) { 
    System.out.println("Number = " + number); 
    } 

    // create an empty array list2 with an initial capacity 
    ArrayList<Integer> arrlist2 = new ArrayList<Integer>(5); 

    // use add() method to add elements in list2 
    arrlist2.add(25); 
    arrlist2.add(30); 
    arrlist2.add(31); 
    arrlist2.add(35); 

    // let us print all the elements available in list2 
    System.out.println("Printing list2:"); 
    for (Integer number : arrlist2) { 
    System.out.println("Number = " + number); 
    } 

    // inserting all elements, list2 will get printed after list1 
    arrlist.addAll(arrlist2); 

    System.out.println("Printing all the elements"); 
    // let us print all the elements available in list1 
    for (Integer number : arrlist) { 
    System.out.println("Number = " + number); 
    } 
    } 
}