How to add in if else statement to validate for string

I am using BlueJ for this assignment I have and I have a problem doing this part of the question which is to put decision constructs to ensure that invalid data is not set which I have already tried.In which I placed the if else statement in the setName portion which does not work. The code will show error if I have put 1 in the GraphicIllustrators main void portion for setName. So where do I need to put the if else statement in the code below.BTW I am using inheritance to do this.So please advise.Thanks!

The coding for the main class:

public class Publishing_Inc
    {
        private int ID=0;
        private String name="-Name Needed-";
        private int level=0;
        private String jobtitle="-Title Needed-";
        private String edit="-Edit Skill-";

public void calculateID(){
    int uniqueID;
    uniqueID =((int)( Math.random()*10000)+1);
    ID = uniqueID;
}
public int getID(){
    return ID;
}



 public void setName(String d) {
name = d;
}
public String getName() {
return name;
}
public void setTitle(String b){
    jobtitle=b;
}
public String getTitle() {
return jobtitle;
}

public void calculatelevel(){
    int uniquelevel;
    uniquelevel =((int)( Math.random()*3)+1);
    level = uniquelevel;
}
public int getlevel() {
return level;
}

public void setEdit(String z){
    edit=z;
}
public String getEdit() {
return edit;
}

}

The sub class:

public class GraphicIllustrators extends Publishing_Inc
{
    public void displayGraphInformation() {
System.out.println("ID: " + getID());
System.out.println("Name:" + getName());
System.out.println("Job Title: " + getTitle());
System.out.println("Level: " + getlevel());
System.out.println();
}

 public static void main (String args[]) {
 GraphicIllustrators graphic = new GraphicIllustrators ( );
graphic.calculateID ( );
graphic.setName (" Tim Cook" );
graphic.calculatelevel ();
graphic.setTitle ("Graphic Illustrators" );
graphic.displayGraphInformation( );
}

}