Java CopyOnWriteArrayList listIterator()用法及代碼示例

• CopyOnWriteArrayList的listIterator()方法以適當的順序返回此列表中元素的listIterator。 listIterator不支持remove，set或add方法。

  用法:

  public ListIterator listIterator()

  參數：該函數不接受任何參數。

  返回值：該函數返回此列表中元素的列表迭代器(按正確順序)

  
  

  以下示例程序旨在說明上述函數：

  示例1:

  // Java Program to illustrate the CopyOnWriteArrayList 
  // iterator() method in Java 
  import java.util.concurrent.CopyOnWriteArrayList; 
  import java.util.*; 
    
  public class GFG { 
      public static void main(String[] args) 
      { 
    
          // create object of CopyOnWriteArrayList 
          CopyOnWriteArrayList<Integer> ArrLis 
              = new CopyOnWriteArrayList<Integer>(); 
    
          // Add elements 
          ArrLis.add(32); 
          ArrLis.add(67); 
          ArrLis.add(67); 
          ArrLis.add(100); 
    
          // print CopyOnWriteArrayList 
          System.out.println("CopyOnWriteArrayList: " + ArrLis); 
    
          // Call listIterator() method of 
          Iterator iteratorVals = ArrLis.listIterator(); 
    
          // Print elements of iterator 
          // created from CopyOnWriteArrayList 
          System.out.println("The iterator values"
                             + " of CopyOnWriteArrayList are:"); 
    
          // prints the elements using an iterator 
          while (iteratorVals.hasNext()) { 
              System.out.println(iteratorVals.next()); 
          } 
      } 
  }

  輸出：

  CopyOnWriteArrayList: [32, 67, 67, 100]
  The iterator values of CopyOnWriteArrayList are:
  32
  67
  67
  100
  

• CopyOnWriteArrayList的listIterator(index)方法從特定索引開始，以適當的順序在此列表中的元素上返回一個listIterator。 listIterator不支持remove，set或add方法。

  用法:

  public ListIterator listIterator(int index)

  參數：該函數接受參數索引，該索引指定要從列表迭代器返回的第一個元素的索引。

  返回值：該函數從指定的索引(以正確的順序)開始，在此列表中的元素上返回列表迭代器。

  異常：如果索引超出範圍，該函數將拋出IndexOutOfBoundsException。

  以下示例程序旨在說明上述函數：

  示例1:

  // Java Program to illustrate the CopyOnWriteArrayList 
  // listIterator() method in Java 
  import java.util.concurrent.CopyOnWriteArrayList; 
  import java.util.*; 
    
  public class GFG { 
      public static void main(String[] args) 
      { 
    
          // create object of CopyOnWriteArrayList 
          CopyOnWriteArrayList<String> ArrLis 
              = new CopyOnWriteArrayList<String>(); 
    
          // Add elements 
          ArrLis.add("gopal"); 
          ArrLis.add("gfg"); 
          ArrLis.add("jgec"); 
          ArrLis.add("sudo"); 
    
          // print CopyOnWriteArrayList 
          System.out.println("CopyOnWriteArrayList: " + ArrLis); 
    
          // Call listIterator() method from 2nd index 
          Iterator iteratorVals = ArrLis.listIterator(2); 
    
          // Print elements of iterator 
          // created from CopyOnWriteArrayList 
          System.out.println("The iterator values"
                             + " of CopyOnWriteArrayList are:"); 
    
          // prints the elements using an iterator 
          while (iteratorVals.hasNext()) { 
              System.out.println(iteratorVals.next()); 
          } 
      } 
  }

  輸出：

  CopyOnWriteArrayList: [gopal, gfg, jgec, sudo]
  The iterator values of CopyOnWriteArrayList are:
  jgec
  sudo
  

  程序2：

  // Java Program to illustrate the CopyOnWriteArrayList 
  // listIterator() method in Java, exception 
  import java.util.concurrent.CopyOnWriteArrayList; 
  import java.util.*; 
    
  public class GFG { 
      public static void main(String[] args) 
      { 
    
          // create object of CopyOnWriteArrayList 
          CopyOnWriteArrayList<String> ArrLis 
              = new CopyOnWriteArrayList<String>(); 
    
          // Add elements 
          ArrLis.add("gopal"); 
          ArrLis.add("gfg"); 
          ArrLis.add("jgec"); 
          ArrLis.add("sudo"); 
    
          // print CopyOnWriteArrayList 
          System.out.println("CopyOnWriteArrayList: " + ArrLis); 
    
          // Call listIterator() method from 6th index 
          // hence exception is returned 
          Iterator iteratorVals = ArrLis.listIterator(6); 
    
          // Print elements of iterator 
          // created from CopyOnWriteArrayList 
          System.out.println("The iterator values"
                             + " of CopyOnWriteArrayList are:"); 
    
          // prints the elements using an iterator 
          while (iteratorVals.hasNext()) { 
              System.out.println(iteratorVals.next()); 
          } 
      } 
  }

  輸出：

  Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 6
      at java.util.concurrent.CopyOnWriteArrayList.listIterator(CopyOnWriteArrayList.java:1107)
      at GFG.main(GFG.java:25)

參考： https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/CopyOnWriteArrayList.html#listIterator–