Question

package data_structures;

import java.util.StringTokenizer;

public class ExpressionEvaluator implements Stack, Queue {
    private String userInput;
    public ExpressionEvaluator() {
        Userinput = null;
    }

    Iterator<E> st = new StringTokenizer();
    token = st.next();
    while (st.hasMoreTokens()) {

The problem has already occured at this point so I’m not continuing the code

The errors:

data_structures/ExpressionEvaluator.java:10: illegal start of typejava
while (st.hasMoreTokens()) {
^
data_structures/ExpressionEvaluator.java:10: <identifier> expected
while (st.hasMoreTokens()) {
^
data_structures/ExpressionEvaluator.java:10: ';' expected
while (st.hasMoreTokens()) {
^
data_structures/ExpressionEvaluator.java:10: illegal start of type
while (st.hasMoreTokens()) {
^
data_structures/ExpressionEvaluator.java:10: <identifier> expected
while (st.hasMoreTokens()) {
^
data_structures/ExpressionEvaluator.java:10: ';' expected
while (st.hasMoreTokens()) {

Answer 1

Following code should be inside a method. Not directly inside a class.

Iterator<E> st = new StringTokenizer();
    token = st.next();
    while (st.hasMoreTokens()) {