如何在Java中迭代 LinkedList？

Java中的 LinkedList 基本上是Java.util 包中存在的集合框架的一部分。它是 LinkedList 数据结构的实现，它以非连续的方式在内存中存储元素。

迭代 LinkedList 的五种方法是：

1. 使用 for 循环
2. 使用while循环
3. 使用增强的 for 循环
4. 使用迭代器
5. 使用 forEach() 方法

方法 1：使用 For循环

Java

// Java program for iterating the LinkedList
// using For loop
  
import java.util.LinkedList;
  
public class GFG {
    public static void main(String[] args)
    {
  
        // Creating a LinkedList of Integer type
        LinkedList linkedList = new LinkedList<>();
  
        // Inserting some Integer values to our LinkedList
        linkedList.add(40);
        linkedList.add(44);
        linkedList.add(80);
        linkedList.add(9);
  
        // LinkedList after insertions: [40, 44, 80, 9]
  
        // Calling the function to iterate our LinkedList
        iterateUsingForLoop(linkedList);
    }
  
    // Function to iterate the LinkedList using a simple for
    // loop
    public static void
             iterateUsingForLoop(LinkedList linkedList)
    {
  
        System.out.print(
            "Iterating the LinkedList using a simple for loop : ");
  
        for (int i = 0; i < linkedList.size(); i++) {
            System.out.print(linkedList.get(i) + " ");
        }
    }
}

---

输出

Iterating the LinkedList using a simple for loop : 40 44 80 9

方法二：使用while循环

我们可以使用 while 循环以与使用 for 循环非常相似的方式来迭代我们的 LinkedList。

Java

// Java program for iterating the LinkedList
// using while loop
  
import java.util.LinkedList;
  
public class GFG {
    public static void main(String[] args) {
  
        // Creating a LinkedList of Character type
        LinkedList vowels = new LinkedList<>();
  
        // Inserting some Character values to our LinkedList
        vowels.add('a');
        vowels.add('e');
        vowels.add('i');
        vowels.add('o');
        vowels.add('u');
  
        // LinkedList after insertions: ['a', 'e', 'i', 'o', 'u']
  
        // calling the function to iterate our LinkedList
        iterateUsingWhileLoop(vowels);
    }
  
    // Function to iterate our LinkedList using while loop
    public static void iterateUsingWhileLoop(LinkedList vowels){
  
        System.out.print("Iterating the LinkedList using while loop : ");
  
        int i=0;
        
        while(i

输出

Iterating the LinkedList using while loop : a e i o u

方法 3：使用增强的 for 循环

使用增强的 for 循环，我们可以顺序迭代 LinkedList。在我们访问完所有元素后，增强的 for 循环的执行结束。让我们看一个使用增强的 for 循环迭代 LinkedList 的示例。

Java

// Java program for iterating the LinkedList
// using Enhanced For loop
  
import java.util.LinkedList;
  
public class GFG {
    public static void main(String[] args)
    {
  
        // Creating a LinkedList of String type
        LinkedList linkedList = new LinkedList<>();
  
        // Inserting some String values to our LinkedList
        linkedList.add("Geeks");
        linkedList.add("for");
        linkedList.add("Geeks");
  
        // LinkedList after insertions: ["Geeks", "for",
        // "Geeks]
  
        // Calling the function to iterate our LinkedList
        iterateUsingEnhancedForLoop(linkedList);
    }
  
    // Function to display LinkedList using Enhanced for
    // loop
    public static void iterateUsingEnhancedForLoop(LinkedList linkedList)
    {
  
        System.out.print(
            "Iterating the LinkedList using enhanced for loop : ");
  
        for (String listElement : linkedList) {
            System.out.print(listElement + " ");
        }
    }
}

输出

Iterating the LinkedList using enhanced for loop : Geeks for Geeks

方法四：使用迭代器

• 要使用迭代器迭代 LinkedList，我们首先为当前列表创建一个迭代器，并使用next()方法继续打印下一个元素，直到下一个元素存在于 LinkedList 中。
• 我们使用hasNext()方法检查 LinkedList 是否包含下一个元素。

Java

// Java program for iterating the LinkedList
// using Iterator
  
import java.util.Iterator;
  
// Importing LinkedList class from
// java.util package
import java.util.LinkedList;
  
public class GFG {
    public static void main(String[] args) {
  
        // Creating a LinkedList of Integer Type
        LinkedList linkedList = new LinkedList<>();
  
        // Inserting some Integer values to our LinkedList
        linkedList.add(5);
        linkedList.add(100);
        linkedList.add(41);
        linkedList.add(40);
        linkedList.add(7);
  
        // LinkedList after insertions : [5, 100, 41, 40, 7]
  
        // Calling the function to iterate our LinkedList
        iterateUsingIterator(linkedList);
    }
  
    // Function to iterate the Linked List using Iterator
    public static void iterateUsingIterator(LinkedList linkedList){
  
        System.out.print("Iterating the LinkedList using Iterator : ");
  
        // Creating an Iterator to our current LinkedList
        Iterator it = linkedList.iterator();
  
        // Inside the while loop we check if the next element
        // exists or not if the next element exists then we print
        // the next element and move to it otherwise we come out
        // of the loop
        
        // hasNext() method return boolean value
          // It returns true when the next element
          // exists otherwise returns false
        while(it.hasNext()){
  
            // next() return the next element in the iteration
            System.out.print(it.next() + " ");
        }
  
    }
}

输出

Iterating the LinkedList using Iterator : 5 100 41 40 7

方法 5：使用 forEach() 方法

• forEach() 方法是在 Java8 中引入的。
• 它为 Iterable 的每个元素执行指定的任务，直到处理完所有元素或操作抛出异常。

句法：

public void forEach(Consumer action)

Java

// Java program for iterating the LinkedList
// using For Each loop
  
import java.util.LinkedList;
  
public class GFG {
    public static void main(String[] args)
    {
  
        // Creating a LinkedList of Integer Type
        LinkedList linkedList = new LinkedList<>();
  
        // Inserting some Integer values to our LinkedList
        linkedList.add(1);
        linkedList.add(2);
        linkedList.add(3);
        linkedList.add(4);
        linkedList.add(5);
  
        // LinkedList after insertions: [1, 2, 3, 4, 5]
  
        // Calling the function to iterate our LinkedList
        iterateUsingForEach(linkedList);
    }
  
    public static void
            iterateUsingForEach(LinkedList linkedList)
    {
  
        System.out.print(
            "Iterating the LinkedList using for each function : ");
  
        // Calling the forEach function to iterate through
        // all the elements inside the Linked List
        linkedList.forEach(
            (element) -> System.out.print(element + " "));
    }
}

输出

Iterating the LinkedList using for each function : 1 2 3 4 5