Java 中的 Java.util.ArrayList.addall()方法
原文:https://www . geesforgeks . org/Java-util-ArrayList-addall-method-Java/
下面是 Java 中 ArrayList 的 addAll() 方法:
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布尔 addAll(Collection c) : 这个方法按照指定集合的迭代器返回元素的顺序，将指定集合中的所有元素追加到这个列表的末尾。如果在操作过程中修改了指定的集合，则此操作的行为是未定义的(意味着如果指定的集合是此列表，并且此列表是非空的，则此调用的行为是未定义的)。
java Parameters: c : This is the collection containing elements to be added to this list. Exception: NullPointerException : If the specified collection is null```java // Java program to illustrate // boolean addAll(Collection c) import java.io.*; import java.util.ArrayList;
public class ArrayListDemo { public static void main(String args[]) {
// create an empty array list1 with initial // capacity as 5 ArrayList arrlist1 = new ArrayList(5);
// use add() method to add elements in the list arrlist1.add(12); arrlist1.add(20); arrlist1.add(45);
// prints all the elements available in list1 System.out.println("Printing list1:"); for (Integer number : arrlist1) System.out.println("Number = " + number);
// create an empty array list2 with an initial // capacity ArrayList arrlist2 = new ArrayList(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 arrlist1.addAll(arrlist2);
System.out.println("Printing all the elements"); // let us print all the elements available in // list1 for (Integer number : arrlist1) System.out.println("Number = " + number); } } ```
```java Output:Printing list1: Number = 12 Number = 20 Number = 45 Printing list2: Number = 25 Number = 30 Number = 31 Number = 35 Printing all the elements Number = 12 Number = 20 Number = 45 Number = 25 Number = 30 Number = 31 Number = 35
```
布尔 addAll(int index，Collection c): 此方法从指定位置开始，将指定集合中的所有元素插入此列表。它将当前在该位置的元素(如果有)和任何后续元素向右移动(增加它们的索引)。新元素将按照指定集合的迭代器返回的顺序出现在列表中。
java Parameters: index : The index at which to insert the first element from the specified collection. c : This is the collection containing elements to be added to this list. Exception: IndexOutOfBoundsException : If the index is out of range NullPointerException : If the specified collection is null```java // Java program to illustrate // boolean addAll(int index, Collection c) import java.io.*; import java.util.ArrayList;
public class ArrayListDemo { public static void main(String args[]) {
// create an empty array list1 with initial // capacity 5 ArrayList arrlist = new ArrayList(5);
// using add() method to add elements in the // list arrlist.add(12); arrlist.add(20); arrlist.add(45);
// prints 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 arrlist2 = new ArrayList(5);
// use add() method to add elements in list2 arrlist2.add(25); arrlist2.add(30); arrlist2.add(31); arrlist2.add(35);
// prints all the elements available in list2 System.out.println("Printing list2:"); for (Integer number : arrlist2) System.out.println("Number = " + number);
// inserting all elements of list2 at third // position arrlist.addAll(2, arrlist2);
System.out.println("Printing all the elements");
// prints all the elements available in list1 for (Integer number : arrlist) System.out.println("Number = " + number); } } ```
```java Output:Printing list1: Number = 12 Number = 20 Number = 45 Printing list2: Number = 25 Number = 30 Number = 31 Number = 35 Printing all the elements Number = 12 Number = 20 Number = 25 Number = 30 Number = 31 Number = 35 Number = 45
```
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