1 /*
   2  * Copyright (c) 2004, 2018, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package sun.tools.jstat;
  27 
  28 /**
  29  * A class that represents a mathematical expression as a tree structure
  30  * containing operators as interior nodes and operands as leaves. The
  31  * operands can be literals or lazily bound variables.
  32  *
  33  * @author Brian Doherty
  34  * @since 1.5
  35  */
  36 public class Expression {
  37     private static int nextOrdinal;
  38     private boolean debug = Boolean.getBoolean("Expression.debug");
  39     private Expression left;
  40     private Expression right;
  41     private Operator operator;
  42     private int ordinal = nextOrdinal++;
  43     private boolean required = false;
  44 
  45     Expression() {
  46         if (debug) {
  47             System.out.println("Expression " + ordinal + " created");
  48         }
  49     }
  50 
  51     void setLeft(Expression left) {
  52         if (debug) {
  53             System.out.println("Setting left on " + ordinal + " to " + left);
  54         }
  55         this.left = left;
  56         this.left.setRequired(required);
  57     }
  58 
  59     Expression getLeft() {
  60         return left;
  61     }
  62 
  63     void setRight(Expression right) {
  64         if (debug) {
  65             System.out.println("Setting right on " + ordinal + " to " + right);
  66         }
  67         this.right = right;
  68         this.right.setRequired(required);
  69     }
  70 
  71     Expression getRight() {
  72         return right;
  73     }
  74 
  75     void setOperator(Operator o) {
  76         if (debug) {
  77             System.out.println("Setting operator on " + ordinal + " to " + o);
  78         }
  79         this.operator = o;
  80     }
  81 
  82     Operator getOperator() {
  83         return operator;
  84     }
  85 
  86     void setRequired(boolean r) {
  87         this.required = r;
  88         if (left != null) {
  89             left.setRequired(required);
  90         }
  91         if (right != null) {
  92             right.setRequired(required);
  93         }
  94     }
  95 
  96     boolean isRequired() {
  97         return required;
  98     }
  99 
 100     public String toString() {
 101         StringBuilder b = new StringBuilder();
 102         b.append('(');
 103         if (left != null) {
 104             b.append(left.toString());
 105         }
 106         if (operator != null) {
 107             b.append(operator.toString());
 108             if (right != null) {
 109                 b.append(right.toString());
 110             }
 111         }
 112         b.append(')');
 113         return b.toString();
 114     }
 115 }