KickJava   Java API By Example, From Geeks To Geeks.

Java > Open Source Codes > bsh > BSHEnhancedForStatement


1 package bsh;
2
3 // Just testing...
4 import java.util.*;
5
6 /**
7      Implementation of the enhanced for(:) statement.
8      This statement uses BshIterable to support iteration over a wide variety
9      of iterable types. Under JDK 1.1 this statement supports primitive and
10      Object arrays, Vectors, and enumerations. Under JDK 1.2 and later it
11      additionally supports collections.
12
13      @author Daniel Leuck
14      @author Pat Niemeyer
15 */
16 class BSHEnhancedForStatement extends SimpleNode implements ParserConstants
17 {
18     String JavaDoc varName;
19
20     BSHEnhancedForStatement(int id) { super(id); }
21
22     public Object JavaDoc eval( CallStack callstack , Interpreter interpreter )
23         throws EvalError
24     {
25         Class JavaDoc elementType = null;
26         SimpleNode expression, statement=null;
27
28         NameSpace enclosingNameSpace = callstack.top();
29         SimpleNode firstNode =((SimpleNode)jjtGetChild(0));
30         int nodeCount = jjtGetNumChildren();
31         
32         if ( firstNode instanceof BSHType )
33         {
34             elementType=((BSHType)firstNode).getType( callstack, interpreter );
35             expression=((SimpleNode)jjtGetChild(1));
36             if ( nodeCount>2 )
37                 statement=((SimpleNode)jjtGetChild(2));
38         } else
39         {
40             expression=firstNode;
41             if ( nodeCount>1 )
42                 statement=((SimpleNode)jjtGetChild(1));
43         }
44
45         BlockNameSpace eachNameSpace = new BlockNameSpace( enclosingNameSpace );
46         callstack.swap( eachNameSpace );
47
48         final Object JavaDoc iteratee = expression.eval( callstack, interpreter );
49
50         if ( iteratee == Primitive.NULL )
51             throw new EvalError("The collection, array, map, iterator, or " +
52                 "enumeration portion of a for statement cannot be null.",
53                 this, callstack );
54
55         CollectionManager cm = CollectionManager.getCollectionManager();
56         if ( !cm.isBshIterable( iteratee ) )
57             throw new EvalError("Can't iterate over type: "
58                 +iteratee.getClass(), this, callstack );
59         BshIterator iterator = cm.getBshIterator( iteratee );
60         
61         Object JavaDoc returnControl = Primitive.VOID;
62         while( iterator.hasNext() )
63         {
64             try {
65             if ( elementType != null )
66                 eachNameSpace.setTypedVariable(
67                     varName/*name*/, elementType/*type*/,
68                     iterator.next()/*value*/, new Modifiers()/*none*/ );
69             else
70                 eachNameSpace.setVariable( varName, iterator.next(), false );
71             } catch ( UtilEvalError e ) {
72                 throw e.toEvalError(
73                     "for loop iterator variable:"+ varName, this, callstack );
74             }
75
76             boolean breakout = false; // switch eats a multi-level break here?
77 if ( statement != null ) // not empty statement
78 {
79                 Object JavaDoc ret = statement.eval( callstack, interpreter );
80
81                 if (ret instanceof ReturnControl)
82                 {
83                     switch(((ReturnControl)ret).kind)
84                     {
85                         case RETURN:
86                             returnControl = ret;
87                             breakout = true;
88                             break;
89
90                         case CONTINUE:
91                             break;
92
93                         case BREAK:
94                             breakout = true;
95                             break;
96                     }
97                 }
98             }
99
100             if (breakout)
101                 break;
102         }
103
104         callstack.swap(enclosingNameSpace);
105         return returnControl;
106     }
107 }
108
Popular Tags