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import java.util.ArrayList;
import java.io.IOException;
public class Infix {
private ArrayList<Character> chars;
private int index;
public static void main(String[] args) {
String str = "+++12-835";
if (args.length > 0) {
str = args[0];
}
try {
Infix parser = new Infix(str);
} catch (Exception e) {
System.out.println("error");
}
}
public Infix(String terminals) throws IOException {
this.index = 0;
this.chars = new ArrayList<Character>();
for (char c: terminals.toCharArray())
this.chars.add(c);
this.list();
if (this.index < this.chars.size())
throw new IOException("Could not parse entire string");
System.out.println();
}
private void list() throws IOException {
char lookahead = this.lookahead();
if (lookahead == '+' || lookahead == '-') {
match(lookahead);
System.out.write('(');
list();
System.out.write(lookahead);
list();
System.out.write(')');
}
else if (lookahead >= '0' && lookahead <= '9')
digit();
else
throw new IOException("Expected lookahead to be a digit or plus/minus");
}
private void digit() throws IOException {
char lookahead = this.lookahead();
if (lookahead >= '0' && lookahead <= '9') {
match(lookahead);
System.out.write(lookahead);
return;
}
throw new IOException("Expected lookahead to be a digit");
}
private void match(char t) throws IOException {
boolean matches = this.lookahead() == t;
if (matches)
this.index += 1;
else if (!matches)
throw new IOException("Expected " + (char)this.lookahead() + " to match " + (char)t);
}
private char lookahead() {
return this.chars.get(this.index);
}
}
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