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Programming in Java Netbeans - A Step by Step Tutorial for Beginners: Lesson 19

Updated on October 16, 2019
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Danson Wachira is a certified Trainer in Computer Science, Information Technology and related studies.

Lesson 19: String methods in Java – toUpperCase() and toLowerCase()

Welcome to lesson 19 of this tutorial on Programming in Java. Having looked into arrays in Java in our previous lessons and how we can manipulate arrays in Java, in this particular lesson we shall look at how we can take advantage of the many methods that ship in with Java to manipulate data of string type. In particular, we shall look at methods to convert strings into uppercase and lowercase.

Unlike int variables, or double variables, strings variables are objects, that means you can manipulate data of string type in more different ways than you can do with other data types such as int, double, boolean, byte, single, char or float variables.

Source

Strings in Java are represented by series of Unicode characters under a variable name and Unicode values are stored as hexadecimals numbers.

Capital letters (A to Z) are stored using hexadecimals values \u0041 to \u005a, while lowercase letters (a to z) are stored using hexadecimals values \u0061 to \u007a.

How to convert strings into uppercase in Java

To convert strings into uppercase in Java, we use the inbuilt toUpperCase() method in Java. Let us write a simple program in Java that stores string characters in lowercase and then use the method to convert the strings into uppercase. Create a new Java class called ChangeToUpper and write the following code.

Program to convert strings into uppercase in Java

In the above program, we have defined a variable of string type called mystring using the following statement.

String mystring = "How are you";

In the first output using JoptionPane, we output the string as it is i.e "How are you". In the second output we first convert the string into uppercase and then output the same string but in uppercase.

JOptionPane.showMessageDialog(null, mystring);

mystring = mystring.toUpperCase();

JOptionPane.showMessageDialog(null, mystring);

How to convert strings into lowercase in Java

Now, modify the program or create another Java class called ChangeToLower as shown above. Change the string variable to be in uppercase and then use the method toLowerCase() to convert the string into lowercase and output. In the next lesson, we shall learn how we can compare strings in Java.

<< Lesson 18 | Lesson 20 >>

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    • profile image

      Stephen 

      7 years ago

      Great tutorial, very useful!!

    • dwachira profile imageAUTHOR

      Danson Wachira 

      7 years ago from Nairobi, Kenya

      Thanks teaches12345 for stopping here and commenting, i really appreciate you support here. Enjoy your day.

    • teaches12345 profile image

      Dianna Mendez 

      7 years ago

      Your hubs are beyond me on this language, but I am in support of the information that you share so freely to help others.

    • dwachira profile imageAUTHOR

      Danson Wachira 

      7 years ago from Nairobi, Kenya

      I think i should work on a language translator in Java, sounds like a fun project, thanks Lord De Cross for the visit and comment. Enjoy your day!

    • Lord De Cross profile image

      Joseph De Cross 

      7 years ago from New York

      Powerful use of the inbuilt toUpperCase() method my friend! I wonder if this can be use to convert into another language. I think all is possible after all. For instance, we could modify the program or create another Java class called ChangeToSwahili?

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