context.java~7~

来自「《深入浅出设计模式》的完整源代码」· JAVA~7~ 代码 · 共 45 行

package littlecompiler;
import java.util.*;
public class Context {
  private StringTokenizer tokenizer;
  private String currentToken;

  public Context (String text) {
    tokenizer = new StringTokenizer (text);
    nextToken ();
  }

  public String nextToken () {
    if (tokenizer.hasMoreTokens ()) {
      currentToken = tokenizer.nextToken();
    }
    else {
      currentToken = null;
    }
    return currentToken;
  }

  public String currentToken () {
    return currentToken;
  }

  public void skipToken (String token) {
    if (!token.equals (currentToken)) {
      System.err.println ("Warning: " + token + " is expected, but " +
                          currentToken + " is found.");
    }
    nextToken ();
  }

  public int currentNumber () {
    int number = 0;
    try {
      number = Integer.parseInt (currentToken);
    }
    catch (NumberFormatException e) {
      System.err.println ("Warning: " + e);
    }
    return number;
  }
}