问这个java程序有什么错？怎么改才对？

方法中声明的变量，在声明的时候必须赋初始值。类成员变量不需要
public class InitializationDemo{
int score = 100;

public String isExcellent(){
String result=null; //这句声明时候必须赋初始值

if(score>=90)
result = "Very very good!";

return result;
}

public static void main(String[] args){
InitializationDemo obj = new InitializationDemo();
System.out.print(obj.isExcellent());
}
}

public class InitializationDemo{
int score = 100;

public String isExcellent(){
String result = null;

if(score>=90)
result = "Very very good!";

return result;
}

public static void main(String[] args){
InitializationDemo obj = new InitializationDemo();
System.out.print(obj.isExcellent());
}
}