How to use contains in java

The contains() method in Java checks whether the specified element or substring exists in the collection or string, and returns a Boolean value: Usage: boolean contains(Object element) Return value: The collection contains elements and returns true. Otherwise, return false. Note: Use equals() and indexOf() methods for comparison. The time complexity is O(n)

contains in Java Usage of ()

contains() method in Java is used to check whether a collection (such as a list, array or string) contains a specific element or substring .

Usage:

contains() The syntax of the method is as follows:

<code class="java">boolean contains(Object element)</code>

Among them:

• element is the element or substring you are looking for in the collection.

Return value:

The method returns a Boolean value indicating whether the specified element or substring is contained in the collection:

• If the collection contains the element or substring, return true.
• Otherwise, return false.

Example:

List:

<code class="java">List<String> names = new ArrayList<>();
names.add("John");
names.add("Mary");
names.add("Bob");

System.out.println(names.contains("John")); // 输出：true
System.out.println(names.contains("Alice")); // 输出：false</code>

Array:

<code class="java">int[] numbers = {1, 2, 3, 4, 5};

System.out.println(Arrays.asList(numbers).contains(3)); // 输出：true
System.out.println(Arrays.asList(numbers).contains(6)); // 输出：false</code>

String:

<code class="java">String text = "Hello World";

System.out.println(text.contains("World")); // 输出：true
System.out.println(text.contains("Java")); // 输出：false</code>

Notes:

• For collections, contains() method Use the equals() method to compare elements.
• For strings, the contains() method uses the indexOf() method to find substrings.
• contains() The time complexity of the method is O(n), where n is the number of elements in the collection.

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