Java Collections fill()用法及代码示例

java.util.Collections类的fill()方法用于将指定列表的所有元素替换为指定元素。

此方法以线性时间运行。

用法:

public static  void fill(List list, T obj)

参数：该方法将以下参数作为参数

• list –用指定元素填充的列表。
  obj –用来填充指定列表的元素。

  以下示例说明了fill()方法

  示例1:

  // Java program to demonstrate 
  // fill() method 
  // for String value 
    
  import java.util.*; 
    
  public class GFG1 { 
      public static void main(String[] argv) throws Exception 
      { 
          try { 
    
              // creating object of List<Integer> 
              List<String> arrlist = new ArrayList<String>(); 
    
              // Adding element to srclst 
              arrlist.add("A"); 
              arrlist.add("B"); 
              arrlist.add("C"); 
    
              // print the elements 
              System.out.println("List elements before fill: "
                                 + arrlist); 
    
              // fill the list 
              Collections.fill(arrlist, "TAJMAHAL"); 
    
              // print the elements 
              System.out.println("\nList elements after fill: "
                                 + arrlist); 
          } 
    
          catch (IllegalArgumentException e) { 
              System.out.println("Exception thrown : " + e); 
          } 
    
          catch (NoSuchElementException e) { 
              System.out.println("Exception thrown : " + e); 
          } 
      } 
  }

  输出：

  List elements before fill: [A, B, C]
  
  List elements after fill: [TAJMAHAL, TAJMAHAL, TAJMAHAL]
  

  示例2:

  // Java program to demonstrate 
  // fill() method 
  // for Integer value 
    
  import java.util.*; 
    
  public class GFG1 { 
      public static void main(String[] argv) throws Exception 
      { 
          try { 
    
              // creating object of List<Integer> 
              List<Integer> arrlist = new ArrayList<Integer>(); 
    
              // Adding element to srclst 
              arrlist.add(20); 
              arrlist.add(30); 
              arrlist.add(40); 
    
              // print the elements 
              System.out.println("List elements before fill: "
                                 + arrlist); 
    
              // fill the list 
              Collections.fill(arrlist, 500); 
    
              // print the elements 
              System.out.println("\nList elements after fill: "
                                 + arrlist); 
          } 
    
          catch (IllegalArgumentException e) { 
              System.out.println("Exception thrown : " + e); 
          } 
    
          catch (NoSuchElementException e) { 
              System.out.println("Exception thrown : " + e); 
          } 
      } 
  }

  输出：

  List elements before fill: [20, 30, 40]
  
  List elements after fill: [500, 500, 500]