The Java String toLowerCase() returns a string which is result of converting all characters in given string to lowercase.
1. String toLowerCase() method
Use String.toLowerCase()
converts any string to lowercase letters.
1.1. Method syntax
String toLowerCase()
method is overloaded and comes in two variants.
/** * @param locale - locale use the case transformation rules for given locale * * @return - string converted to lowercase */ public String toLowerCase(); public String toLowerCase(Locale locale);
1.2. ‘null’ is not valid method argument
Method does not accept 'null'
argument. It will throw NullPointerException
in case method argument is null.
Exception in thread "main" java.lang.NullPointerException at java.lang.String.toLowerCase(String.java:2710) at com.StringExample.main(StringExample.java:11)
2. Java convert string to lowercase example
Java program to convert the string to lowercase using default locale rules.
public class StringExample { public static void main(String[] args) { String string = "Hello World"; String lowercaseString = string.toLowerCase(); System.out.println(lowercaseString); } }
Program output.
hello world
toLowerCase()
method is equal to callingtoLowerCase(Locale.getDefault())
.
3. Java String toLowerCase(Locale locale) example
Java program to convert the string to lowercase using default locale rules.
public class StringExample { public static void main(String[] args) { System.out.println("hello world".toLowerCase(Locale.getDefault())); System.out.println("Γειά σου Κόσμε".toLowerCase(Locale.US)); } }
Program output.
hello world γειά σου κόσμε
In this example, we learned to convert string to lowercase.
References:
A Guide to Java String
String Java Doc