Java String contains()

class Main {
  public static void main(String[] args) {
    String str1 = "Java String contains()";

    // check if str1 contains "Java"
    boolean result = str1.contains("Java");

    System.out.println(result);
  }
}

// Output: true

Syntax of contains()

The syntax of the String contains() method is:

string.contains(CharSequence ch)

Here, string is an object of the String class.

contains() Parameters

The contains() method takes a single parameter.

• ch (charSequence) - a sequence of characters

Note: A charSequence is a sequence of characters such as: String, CharBuffer, StringBuffer etc.

contains() Return Value

• returns true if the string contains the specified character
• returns false if the string doesn't contain the specified character

Example 1: Java String contains()

class Main {
  public static void main(String[] args) {
    String str1 = "Learn Java";
    Boolean result;

    // check if str1 contains "Java"
    result = str1.contains("Java");
    System.out.println(result);  // true

    // check if str1 contains "Python"
    result = str1.contains("Python");
    System.out.println(result);  // false

    // check if str1 contains ""
    result = str1.contains("");

    System.out.println(result);  // true
  }
}

Here, str.contains("") gives true because the empty string is a subset of every other string.

Example 2: Using contains() With if...else

class Main {
  public static void main(String[] args) {
    String str1 = "Learn Java";
    String str2 = "Java";
    String str3 = "java";
    Boolean result;
    
    // true because "Learn Java" contains "Java"
    if (str1.contains(str2)) {

      System.out.println(str1 + " contains " + str2);
    }
    else {
      System.out.println(str1 + " doesn't contains " + str2);
    }
    
    // contains() is case-sensitive
    // false because "Learn Java" doesn't contains "java"
    if (str1.contains(str3)) {

      System.out.println(str1 + " contains " + str3);
    }
    else {
      System.out.println(str1 + " doesn't contain " + str3);
    }
  }
}

Output

Learn Java contains Java
Learn Java doesn't contain java