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Java > Open Source Codes > org > objectstyle > cayenne > exp > ASTStack


1 /* ====================================================================
2  *
3  * The ObjectStyle Group Software License, version 1.1
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54  * <http://objectstyle.org/>.
55  */
56 package org.objectstyle.cayenne.exp;
57
58 import java.util.LinkedList JavaDoc;
59
60 /**
61  * AST evaluation stack.
62  *
63  * @author Andrei Adamchik
64  * @since 1.0.6
65  */
66 final class ASTStack extends LinkedList JavaDoc {
67     static boolean booleanFromObject(Object JavaDoc object) {
68         // TODO: pull conversion to boolean to utils, or use 3rd party converter
69 if (object instanceof Boolean JavaDoc) {
70             return ((Boolean JavaDoc) object).booleanValue();
71         }
72
73         if (object instanceof Number JavaDoc) {
74             return ((Number JavaDoc) object).intValue() != 0;
75         }
76
77         return object != null;
78     }
79
80     /**
81       * Pops a value from the stack.
82       */
83     Object JavaDoc pop() {
84         return remove(size() - 1);
85     }
86
87     /**
88      * Pops a value from the stack, converting it to boolean.
89      */
90     boolean popBoolean() {
91         Object JavaDoc obj = pop();
92         return booleanFromObject(obj);
93     }
94
95     /**
96      * Pops a value from the stack, casting it to Comparable.
97      */
98     Comparable JavaDoc popComparable() {
99         return (Comparable JavaDoc) pop();
100     }
101
102     /**
103      * Pops a value from the stack, converting it to int.
104      */
105     int popInt() {
106         return ((Integer JavaDoc) pop()).intValue();
107     }
108
109     /**
110      * Returns a value from the stack without removing it.
111      */
112     public Object JavaDoc peekObject() {
113         return get(size() - 1);
114     }
115
116     /**
117      * Returns a value from the stack without removing it, converting it to boolean.
118      */
119     boolean peekBoolean() {
120         Object JavaDoc obj = peekObject();
121         return booleanFromObject(obj);
122     }
123
124     /**
125      * Returns a value from the stack without removing it, converting it to int.
126      */
127     int peekInt() {
128         return ((Integer JavaDoc) peekObject()).intValue();
129     }
130
131     /**
132      * Pushes a value to the stack.
133      */
134     void push(Object JavaDoc obj) {
135         add(obj);
136     }
137
138     /**
139      * Pushes a boolean value to the stack.
140      */
141     void push(boolean b) {
142         add(b ? Boolean.TRUE : Boolean.FALSE);
143     }
144 }
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