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1
50 package org.apache.avalon.excalibur.collections;
51
52
60 public final class FixedSizeBuffer implements Buffer
61 {
62 private final Object  [] m_elements;
63 private int m_start = 0;
64 private int m_end = 0;
65 private boolean m_full = false;
66
67 public FixedSizeBuffer( int size )
68 {
69 m_elements = new Object [ size ];
70 }
71
72 public FixedSizeBuffer()
73 {
74 this( 32 );
75 }
76
77 public final int size()
78 {
79 int size = 0;
80
81 if( m_end < m_start )
82 {
83 size = m_elements.length - m_start + m_end;
84 }
85 else if( m_end == m_start )
86 {
87 size = ( m_full ? m_elements.length : 0 );
88 }
89 else
90 {
91 size = m_end - m_start;
92 }
93
94 return size;
95 }
96
97 public final boolean isEmpty()
98 {
99 return size() == 0;
100 }
101
102 public final void add( Object element )
103 {
104 if( null == element )
105 {
106 throw new NullPointerException ( "Attempted to add null object to buffer" );
107 }
108
109 if( m_full )
110 {
111 throw new BufferOverflowException( "The buffer cannot hold more than "
112 + m_elements.length + " objects." );
113 }
114
115 m_elements[ m_end++ ] = element;
116
117 if( m_end >= m_elements.length )
118 {
119 m_end = 0;
120 }
121
122 if( m_end == m_start )
123 {
124 m_full = true;
125 }
126 }
127
128 public final Object remove()
129 {
130 if( isEmpty() )
131 {
132 throw new BufferUnderflowException( "The buffer is already empty" );
133 }
134
135 Object element = m_elements[ m_start ];
136
137 if( null != element )
138 {
139 m_elements[ m_start++ ] = null;
140
141 if( m_start >= m_elements.length )
142 {
143 m_start = 0;
144 }
145
146 m_full = false;
147 }
148
149 return element;
150 }
151 }
152 |
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