String Characters Display First Three Multiple Times

I am trying below challenge to display first three characters three times if the size of the string is greater than 3.

Say if i send hello i should get helhelhel

if i send xyz i should get xyzxyzxyz

I wrote as below

public String front3(String str) {
if(str.length()==3){
return str+str+str;
}
if(str.length()>3){
String str2=new String(new char[]{str.charAt(0),str.charAt(1),str.charAt(2)});
return str2;
}
}

I am getting error as below

Error:public String front3(String str) {
^^^^^^^^^^^^^^^^^^
This method must return a result of type String

Possible problem: the if-statement structure may theoretically allow a run to reach the end of the method without calling return. Consider adding a last line in the method return some_value; so a value is always returned.