java 在java中附加arraylist
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Appending arraylist in java
提问by thetna
Is it possible to concatenate two or more arraylist ? I have following case:
是否可以连接两个或多个 arraylist ？我有以下案例：
private Arraylist<Double> getContextVectorsize(int sizeContext){
ArrayList<Double> contextList = new ArrayList<Double>();
for(int i =0 ; i< sizeContext; i++){
contextList = //TODO
}
}
I would like to append all the arraylist in order and want to generate an arraylist of
size = sizeContext*ArraylistOfSingleMember
我想按顺序附加所有的数组列表，并希望生成一个数组列表
size = sizeContext*ArraylistOfSingleMember
回答by lrAndroid
You could use the addAll() method.
您可以使用 addAll() 方法。
回答by user2243632
Use list1.addAll(list2), this returns true if it worked AND updates list1. Here is a full code example from tutorialspoint.com.
使用 list1.addAll(list2)，如果它有效并更新 list1，则返回 true。这是来自 tutorialspoint.com 的完整代码示例。
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);
}
}
}
回答by Jakub Zaverka
for(int i =0 ; i< sizeContext; i++){
contextList.addAll( an instance of ArrayList<Double>);
}
