Java中的 ArrayList get(index) 方法及示例

Java中ArrayList的get()方法用于获取列表中指定索引的元素。

句法：

get(index)

参数：要返回的元素的索引。它是 int 数据类型。

返回类型：给定列表中指定索引处的元素。

异常：如果索引超出范围，则抛出 IndexOutOfBoundsException (index=size())

Note: Time Complexity: ArrayList is one of the List implementations built a top an array. Hence, get(index) is always a constant time O(1) operation.

例子：

Java

// Java Program to Demonstrate the working of
// get() method in ArrayList
 
// Importing ArrayList class
import java.util.ArrayList;
 
// Main class
public class GFG {
 
    // Main driver method
    public static void main(String[] args)
    {
        // Creating an Empty Integer ArrayList
        ArrayList arr = new ArrayList(4);
 
        // Using add() to initialize values
        // [10, 20, 30, 40]
        arr.add(10);
        arr.add(20);
        arr.add(30);
        arr.add(40);
 
        // Printing elements of list
        System.out.println("List: " + arr);
 
        // Getting element at index 2
        int element = arr.get(2);
 
        // Displaying element at specified index
        // on console inside list
        System.out.println("the element at index 2 is "
                           + element);
    }
}

输出

List: [10, 20, 30, 40]
the element at index 2 is 30

示例 2 ：演示错误的程序

Java

// Java Program to Demonstrate Error Generated
// while using get() method in ArrayList
 
// Importing ArrayList class
import java.util.ArrayList;
 
// Main class
public class GFG {
 
    // Main driver method
    public static void main(String[] args)
    {
        // Creating an Empty Integer ArrayList
        ArrayList arr = new ArrayList(4);
 
        // Using add() method to insert elements
        // and adding custom values
        arr.add(10);
        arr.add(20);
        arr.add(30);
        arr.add(40);
 
        // Getting element at index 2
        int element = arr.get(5);
 
        // Print all the elements of ArrayList
        System.out.println("the element at index 2 is "
                           + element);
    }
}

输出 ：

Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 5, Size: 4
    at java.util.ArrayList.rangeCheck(ArrayList.java:657)
    at java.util.ArrayList.get(ArrayList.java:433)
    at GFG.main(GFG.java:22)