data_structures/ExpressionEvaluator.java:14: incompatible types.lang.String)
found : java.util.StringTokenizer class data_structures.ExpressionEvaluator
required: java.util.Iterator<java.lang.String>ing> st = StringTokenize
Iterator<String> st = new StringTokenizer(s);
Iterator をどこかで宣言する必要がありますか?