VerboseStack.java

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package aud.example;
 
import java.util.NoSuchElementException;
import aud.Stack;
 
public class VerboseStack<T> extends Stack<T> {
 
  int height_ = 0;
 
  public VerboseStack() {}
 
  @Override public T pop() throws NoSuchElementException {
    T x=super.pop();
    --height_;
    print("pop "+x);
    return x;
  }
 
  @Override public void push(T x) {
    super.push(x);
    print("push "+x);
    ++height_;
  }
 
  private void print(String message) {
    for (int i=0;i<height_;++i)
      System.err.print(" ");
    System.err.println(message+" => "+toString());
  }
 
  @Override
  public String toString() {
    if (!is_empty()) {
      T x=super.pop();
      String bottom=toString();
      super.push(x);
      return (bottom+(bottom.length()>1 ? "|":""))+x;
    }
    else
      return "|";
  }
 
};