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Module - 6 Arrays and String Part 2

2026-03-31 17:26

Tags: #java

Author: Duke Hsu

String Method

  • The String class has a set of built-in methods that you can use on strings.
  • In java ,Strings are immutable
  • In java, a string is a sequence of characters
  • Every character in a string has an index starting from 0
  • A string can be treated as an array of characters.

Key String Methods

Method Description Return Data Type Note
length(); return characters size int
toUpperCase(); return characters in all CAPS String
toLowerCase(); return characters in all lowercase String
chartAt(); return the character of the specified (position) char
codePointAt(); Returns the Unicode of the character at the specified index int
codePointCount(); Returns the number of Unicode values found in a string. int
substring(startIdex); Returns a new string which is the substring of a specified string String argument datatype is int
substring(startIndex, endIndex); Returns a new string which is the substring of a specified string String argument datatype is int
equals(); compare tow string equal or not true or false boolean case sensitive
contains(); check whether a string contains a sequence of characters boolean
replace(); Searches a string for a specified value, and returns a new string where the specified values are replaced String
replaceAll(); Replaces each substring of this string that matches the given regular expression with the given replacement String regex
isEmpty(); Checks whether a string is empty or not . boolean

Code Example

java_string_methods

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package javaString;
public class Main {
    public static void main(String[] args) {

            String country = "Philippines";

            boolean result = country.equals("Taiwan"); //false
            int result = country.length(); //11
            char result = country.charAt(6); //p
            int result = country.indexOf("n"); //8
            boolean result = country.isEmpty();//false
            String result = country.toUpperCase(); //PHILIPPINES
            String result = country.toLowerCase(); //philippines
            String result = country.substring(3); //lippines
            String result = country.substring(2,8); //ilippi
            boolean result = country.contains("P"); //true
            String result = country.replace("s", "z"); //Philippinez

            System.out.println("The reults is :  "+ result);


    }

}

References

https://www.w3schools.com/java/java_ref_string.asp