Java Collections.nCopies()用法及代碼示例

Collections.nCopies()的作用是返回一個不可變的列表，其中包含給定對象的n個副本。如果我們要創建具有給定對象的n個副本的列表，則此函數很有幫助。新分配的數據對象很小，即它包含對數據對象的單個引用。

用法:

public static <T> List<T> nCopies(int number, T object)

where, number is the number of copies
of object and object represents the 
element which will appear number times
in the returned list. T represents generic type.

異常：如果number的值小於0，則該函數引發IllegalArgumentException。

例：

Java

// Java code to show implementation 
// of Collections.nCopies() 
import java.util.*; 
  
class GFG { 
  
    // Driver code 
    public static void main(String[] args) 
    { 
  
        // creating a list where first argument 
        // represents the number of copies and 
        // the second argument represents the 
        // element to be copied for 'number' times 
        // This will create 4 copies of the objects. 
        List list = Collections.nCopies(4, "GeeksforGeeks"); 
  
        // Displaying the list returned 
        System.out.println("The list returned is :"); 
        Iterator itr = list.iterator(); 
        while (itr.hasNext()) { 
            System.out.print(itr.next() + " "); 
        } 
        System.out.println("\n"); 
  
        List list1 = Collections.nCopies(3, "GeeksQuiz"); 
      
        // Displaying the list returned 
        System.out.println("The list returned is :"); 
        Iterator itr1 = list1.iterator();   
        while (itr1.hasNext()) { 
            System.out.print(itr1.next() + " "); 
        } 
        System.out.print("\n"); 
    } 
}

輸出：

The list returned is :
GeeksforGeeks GeeksforGeeks GeeksforGeeks GeeksforGeeks 

The list returned is :
GeeksQuiz GeeksQuiz GeeksQuiz

相關用法

注：本文由純淨天空篩選整理自Sahil_Bansall大神的英文原創作品 Collections.nCopies() in Java。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。