Need help with creating a linked list

Question

I need to create a linked list that i can put numbers or an operator into
class Number_or_op
boolean flag;
double number;
char operator;
Number_or_op(boolean flag1,double number1,char operator1)
flag = flag1;
number = number1;
operator = operator1;
class Expr {
Number_or_op first;
Expr rest;
Expr(Number_or_op first1,Expr rest1)
first = first1;
rest = rest1;
how do i make a linked list out of this? im trying
Expr list1 = new Expr(3, new Expr('*' , new Expr(4 , null)));
but keep getting an error D:\Documentation\expr.java:14: internal error; cannot instantiate Expr.<init> at Expr to ()
how do i fix the number_or_op so it can make it into a list?

Answer 1

Let me reitterate my problem because i am so lost...
I am used to making linked list using an integers only.. and now my teacher wants me to use both integers and chars, the chars being operators..
I have no idea how to do that using hte code he provided because it makes no sense at all to me
class Number_or_op
boolean flag;
double number;
char operator;
Number_or_op(boolean flag1,double number1,char operator1)
flag = flag1;
number = number1;
operator = operator1;
class Expr {
Number_or_op first;
Expr rest;
Expr(Number_or_op first1,Expr rest1)
first = first1;
rest = rest1;
I need to make a list that looks like 1 + 3 / 4 each operator or number needs a different node.. i just cant think of how to do it and keep getting an error message everytime i do saying:
File: D:\Documentation\expr.java [line: 14]
Error: D:\Documentation\expr.java:14: internal error; cannot instantiate Expr.<init> at Expr to ()
I just dont know what to do