Java Arraylist.contains()用法及代碼示例

Java中的ArrayList contains()方法用於檢查指定元素是否存在於給定列表中。

用法:

public boolean contains(Object)
object-element to be searched for

參數：
object用於在此列表中檢查是否存在

返回值：
如果在列表中找到指定的元素，則返回true，否則返回false。

代碼1：以整數形式演示contains()方法的用法

// Java code to demonstrate the working of 
// contains() method in ArrayList 
  
// for ArrayList functions 
import java.util.ArrayList; 
  
class GFG { 
    public static void main(String[] args) 
    { 
  
        // creating an Empty Integer ArrayList 
        ArrayList<Integer> arr = new ArrayList<Integer>(4); 
  
        // using add() to initialize values 
        // [1, 2, 3, 4] 
        arr.add(1); 
        arr.add(2); 
        arr.add(3); 
        arr.add(4); 
  
        // use contains() to check if the element 
        // 2 exits or not 
        boolean ans = arr.contains(2); 
  
        if (ans) 
            System.out.println("The list contains 2"); 
        else
            System.out.println("The list does not contains 2"); 
  
        // use contains() to check if the element 
        // 5 exits or not 
        ans = arr.contains(5); 
  
        if (ans) 
            System.out.println("The list contains 5"); 
        else
            System.out.println("The list does not contains 5"); 
    } 
}

輸出：

The list contains 2
The list does not contains 5

代碼2：在字符串中演示contains()方法的用法

// Java code to demonstrate the working of 
// contains() method in ArrayList of string 
  
// for ArrayList functions 
import java.util.ArrayList; 
  
class GFG { 
    public static void main(String[] args) 
    { 
  
        // creating an Empty String ArrayList 
        ArrayList<String> arr = new ArrayList<String>(4); 
  
        // using add() to initialize values 
        // ["geeks", "for", "geeks"] 
        arr.add("geeks"); 
        arr.add("for"); 
        arr.add("geeks"); 
  
        // use contains() to check if the element 
        // "geeks" exits or not 
        boolean ans = arr.contains("geeks"); 
  
        if (ans) 
            System.out.println("The list contains geeks"); 
        else
            System.out.println("The list does not contains geeks"); 
  
        // use contains() to check if the element 
        // "coding" exits or not 
        ans = arr.contains("coding"); 
  
        if (ans) 
            System.out.println("The list contains coding"); 
        else
            System.out.println("The list does not contains coding"); 
    } 
}

輸出：

The list contains geeks
The list does not contains coding

實際應用：
在搜索操作中，我們可以檢查列表中是否存在給定元素。

參考：
Oracle Docs

相關用法

注：本文由純淨天空篩選整理自Striver大神的英文原創作品 Arraylist.contains() in Java。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。