Java集合 emptyListIterator() 方法和示例
Java Collections 的emptyListIterator()方法是一种用于迭代Java中没有元素的 List 的方法。
语法:
public static ListIterator emptyListIterator()
参数:它没有参数。
返回类型:它将返回带有空元素的列表。
例外:
- NoSuchElementException –这将在给定集合中未找到给定元素时发生。
示例 1:
Java
// Java program to run the iterator with no elements
import java.util.*;
public class GFG {
// main method
public static void main(String[] args)
{
// create an list iterator
ListIterator iterator
= Collections.emptyListIterator();
// get the elements which is empty
System.out.println(iterator.hasNext());
}
}
Java
// Java program to iterate the elements with a list
// of elements. Here we will get an error
// because the list is not empty
import java.util.*;
public class GFG {
// main method
public static void main(String[] args)
{
// create an array list
List data = new ArrayList();
// add 2 elements into the array list
data.add(100);
data.add(200);
// iterate the elements
ListIterator iterator
= Collections.emptyListIterator();
// display
System.out.println(iterator.next());
}
}
Java
// Java program to display next index
// and previous index element
import java.util.*;
public class GFG {
// main method
public static void main(String[] args)
{
// create an array list
List data = new ArrayList();
// add 2 elements into the array list
data.add(100);
data.add(200);
// iterate the elements
ListIterator iterator
= Collections.emptyListIterator();
System.out.println(iterator.nextIndex());
// display previous element
System.out.println(iterator.previousIndex());
}
}
输出
false
示例 2:
Java
// Java program to iterate the elements with a list
// of elements. Here we will get an error
// because the list is not empty
import java.util.*;
public class GFG {
// main method
public static void main(String[] args)
{
// create an array list
List data = new ArrayList();
// add 2 elements into the array list
data.add(100);
data.add(200);
// iterate the elements
ListIterator iterator
= Collections.emptyListIterator();
// display
System.out.println(iterator.next());
}
}
输出:
Exception in thread "main" java.util.NoSuchElementException
at java.util.Collections$EmptyIterator.next(Collections.java:4191)
at GFG.main(GFG.java:12)
示例 3:
用于显示下一个索引和上一个索引元素的Java程序。我们可以通过使用nextIndex()方法来显示下一个索引
语法:
iterator.nextIndex()
要显示上一个索引,
语法:
iterator.previousIndex()
Java
// Java program to display next index
// and previous index element
import java.util.*;
public class GFG {
// main method
public static void main(String[] args)
{
// create an array list
List data = new ArrayList();
// add 2 elements into the array list
data.add(100);
data.add(200);
// iterate the elements
ListIterator iterator
= Collections.emptyListIterator();
System.out.println(iterator.nextIndex());
// display previous element
System.out.println(iterator.previousIndex());
}
}
输出
0
-1