Java find substring in String

The Java String contains() method is used to check whether the specific set of characters are part of the given string or not. It returns a boolean value true if the specified characters are substring of a given string and returns false otherwise. It can be directly used inside the if statement.

Simple Approach: The idea is to run a loop from start to end and for every index in the given string check whether the sub-string can be formed from that index . This can be done by running a nested loop traversing the given string and in that loop run another loop checking for sub-string from every index.

In order to check if a String has only Unicode letters in Java, we use the isDigit() and charAt() methods with decision-making statements . The isLetter(int codePoint) method determines whether the specific character (Unicode codePoint) is a letter. It returns a boolean value, either true or false.

The fastest way to check if a string contains a particular word or substring is with the help of String. indexOf() method . This method returns the index of the first occurrence of the specified substring inside the calling String object.