Make String.format(“%s”, arg) display null-valued arguments differently from “null”

Question

Consider the custom toString() implementation of a bean:

@Override
public String toString() {
    String.format(\"this is %s\", this.someField);
}
<         


        

Answer 1

public static String format(String format, Object... args){
    for (int i=0;i

then use the method ，ok