How to Accumulate results

Hello I am very new to java and am writing a method that shifts each letter in a String over in the alphabet n times. I am having trouble figuring out a way to accumulate the results

Code Java:

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Code:
public String shift(int n){
 
char character; 
 
for (int i = 0; i < text.length(); i++)
{
character = text.charAt(i); 
if(character>='A'&& character<='Z'){
character = (char) (character + n);
if (character>'Z') 
character-=26;
 
// How to accumulate?
text=Character.toString(character);
 
}
 
} 
return text; 
}

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any advice is appreciated! I have been suggested a String builder, but im not quite sure on how to use it, is there a simpler method?

See The StringBuilder Class (The Java™ Tutorials > Learning the Java Language > Numbers and Strings)

Cross posted after being advised to use a StringBuilder at
Accumulation Help - Java Forums

Didn't even have the courtesy to thank the member who made the suggestion.

db