%s Formats an object, generally by calling its toString() method : Formatter « Utility Classes « SCJP

1. SCJP
2. Utility Classes
3. Formatter

import java.util.Formatter;
public class MainClass{
    public static void main(String[] argv){
        StringBuilder sb = new StringBuilder();
        Formatter f = new Formatter(sb);
        MyClass b = new MyClass();
        f.format("The value is %b, so there.", b);
        System.out.println(sb);


    }
}
    
class MyClass{
   public String toString(){
       return "MyClass";
   }
}

The value is true, so there.