Java ArrayList contains() Method
Java ArrayListThe contains() method is used to determine whether an element exists in the dynamic array.
The syntax of the contains() method is:
arraylist.contains(Object obj)
Note:arraylist is an object of the ArrayList class.
Parameter Description:
- obj - The element to be detected
Return Value
Returns true if the specified element exists in the dynamic array.
Returns false if the specified element does not exist in the dynamic array.
Example
A String-type dynamic array using the contains() method:
Example
class Main {
public static void main(String[] args){
// Create an array
ArrayList<String> sites = new ArrayList<>();
sites.add("Google");
sites.add("Example");
sites.add("Taobao");
System.out.println("Website list: " + sites);
// Check if Example is in this array
System.out.print("Does Example exist in arraylist: ");
System.out.println(sites.contains("Example"));
// Check if Weibo is in this array
System.out.print("Does Weibo exist in arraylist: ");
System.out.println(sites.contains("Weibo"));
}
}
Executing the above program outputs the result:
Example 是否存在于 arraylist: true Weibo 是否存在于 arraylist: false
In the above example, we create a dynamic array named sites. Note the expression:
sites.contains("Example")
sites.contains("Weibo")
In the above code, the contains() method checks whether Example exists in the dynamic array. Since Example exists, the method returns true. However, Weibo does not exist in the list, so the method returns false.
Note:The contains() method actually uses the equals() method internally to find elements. If the specified element matches an element in the array, the method returns true.
An Integer-type dynamic array using the contains() method:
Example
class Main {
public static void main(String[] args) {
// Create an array
ArrayList<Integer> numbers = new ArrayList<>();
// Insert elements into the array
numbers.add(2);
numbers.add(3);
numbers.add(5);
System.out.println("Number ArrayList: " + numbers);
// Check if 3 is in this array
System.out.print("Is 3 in arraylist: ");
System.out.println(numbers.contains(3));
// Check if 1 is in this array
System.out.print("Is 1 in arraylist: ");
System.out.println(numbers.contains(1));
}
}
Executing the above program outputs the result:
Number ArrayList: [2, 3, 5] 3 是否在 arraylist: true 1 是否在 arraylist: false
In the above code, the contains() method checks whether 3 exists in the dynamic array. Since 3 exists, the method returns true. However, 1 does not exist in the list, so the method returns false.
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