Java String toUpperCase() Method

toUpperCase() method

The toUpperCase() method of String class is used to convert all the characters in a String to upper case letters.

Syntax - public String toUpperCase()

As per syntax of this method,

Access modifier - toUpperCase() method is a public method.
Parameter passed - No value is passed to it.
Value returned - It returns the upper case String value of a String object on which toUpperCase() method was called..

Method toUpperCase() method when called on any String object, returns its contents as an upper case String. The returned upper case String must be stored or used otherwise it is lost.

Calling toUpperCase() method on a String object.

//Program to convert a String to upper case letters. 


class StringUpper
{
public static void main(String[] ar)
{
String str= new String("new zealand");
System.out.println("Original String is : "+ str);
System.out.println("String's upper case value : " + str.toUpperCase());
}

}

Output is :

String's value : new zealand
String's upper case value : New ZEALAND

new zealand

Method toUpperCase() does not modify the original content in a String object

toUpperCase()

without modifying its original content at all

Let's understand this by an example -:

String

new york

//Program to convert a String to upper case letters. 


class StringUpper
{
public static void main(String[] ar)
{
String str= new String("mars - the red planet");
System.out.println("Original String is : "+ str);
System.out.println("String's upper case value : " + str.toUpperCase());

System.out.println("String value : " + str);
}

}

Output is :

String's value : mars - the red planet
String's upper case value : MARS - THE RED PLANET
String's value : mars - the red planet

mars - the red planet

toUpperCase()

Modifying the original letters of String object with upper case letters

//Program to convert a string to Uppercase letters. 

class StringUpper2
{
public static void main(String[] ar)
{
String str= new String("hurray! it's sunday!");
System.out.println("Original string is : "+ str);

str=str.toUpperCase(); //result of calling toUpperCase() is stored back in String object

System.out.println("String's value after converting to UpperCase : " + str);
}
}

Output is :

Original string is : hurray! it's sunday!
String's value after converting to upper case : HURRAY! IT'S SUNDAY!

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toUpperCase() method

Calling toUpperCase() method on a String object.

Output is :

Method toUpperCase() does not modify the original content in a String object

Output is :

Modifying the original letters of String object with upper case letters

Output is :

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