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Diffstat (limited to 'libjava/classpath/java/beans/Expression.java')
-rw-r--r-- | libjava/classpath/java/beans/Expression.java | 133 |
1 files changed, 133 insertions, 0 deletions
diff --git a/libjava/classpath/java/beans/Expression.java b/libjava/classpath/java/beans/Expression.java new file mode 100644 index 0000000..20b04f1 --- /dev/null +++ b/libjava/classpath/java/beans/Expression.java @@ -0,0 +1,133 @@ +/* java.beans.Expression + Copyright (C) 2004 Free Software Foundation, Inc. + +This file is part of GNU Classpath. + +GNU Classpath is free software; you can redistribute it and/or modify +it under the terms of the GNU General Public License as published by +the Free Software Foundation; either version 2, or (at your option) +any later version. + +GNU Classpath is distributed in the hope that it will be useful, but +WITHOUT ANY WARRANTY; without even the implied warranty of +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +General Public License for more details. + +You should have received a copy of the GNU General Public License +along with GNU Classpath; see the file COPYING. If not, write to the +Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA +02110-1301 USA. + +Linking this library statically or dynamically with other modules is +making a combined work based on this library. Thus, the terms and +conditions of the GNU General Public License cover the whole +combination. + +As a special exception, the copyright holders of this library give you +permission to link this library with independent modules to produce an +executable, regardless of the license terms of these independent +modules, and to copy and distribute the resulting executable under +terms of your choice, provided that you also meet, for each linked +independent module, the terms and conditions of the license of that +module. An independent module is a module which is not derived from +or based on this library. If you modify this library, you may extend +this exception to your version of the library, but you are not +obligated to do so. If you do not wish to do so, delete this +exception statement from your version. */ + + +package java.beans; + +/** + * class Expression + * + * An Expression captures the execution of an object method that + * returns a value. It stores an object, the method to call, and the + * arguments to pass to the method. + * + * @since 1.4 + */ +public class Expression extends Statement +{ + // This is a placeholder to indicate that value hasn't been set + // yet; + private static final Object unset = new Object(); + + // The value to return. This is equal to unset until getValue is called. + private Object value; + + + /** + * Constructor + * + * Constructs an Expression representing the invocation of + * object.methodName(arg[0], arg[1], ...); However, it will never + * be executed. Instead, value will always be returned. + * + * @param value The value to return. + * @param target The object to invoke the method on. + * @param methodName The object method to invoke. + * @param arguments An array of arguments to pass to the method. + */ + public Expression(Object value, Object target, String methodName, + Object[] arguments) + { + super(target, methodName, arguments); + this.value = value; + } + + /** + * Constructor + * + * Constructs an Expression representing the invocation of + * object.methodName(arg[0], arg[1], ...); + * + * @param target The object to invoke the method on. + * @param methodName The object method to invoke. + * @param arguments An array of arguments to pass to the method. + */ + public Expression(Object target, String methodName, Object[] arguments) + { + super(target, methodName, arguments); + this.value = unset; + } + + /** + * Return the result of executing the method. + * + * If the cached value has not yet been set, the method is + * executed in the same way as Statement.execute(), except that + * the value is cached, and then returned. If the value has been + * set, it is returned without executing the method again. + * + * @return the result of executing the method. + * @exception Exception if an error occurs + */ + public Object getValue() throws Exception + { + if (value == unset) + value = doExecute(); + return value; + } + + /** + * Set the cached value to be returned by getValue() + * + * @param value the value to cache and return. + */ + public void setValue(Object value) + { + this.value = value; + } + + /** + * Return a string representation of this expression. + */ + public String toString() + { + String result = super.toString(); + if (value != unset) + return value.getClass().getName() + " " + result; + return result; + } +} |