1 /*
2  * Copyright (C) 2007 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 package com.android.dx.util;
18 
19 /**
20  * Very simple base class that implements a flag to control the mutability
21  * of instances. This class just provides the flag and a utility to check
22  * and throw the right exception, but it is up to subclasses to place calls
23  * to the checker in all the right places.
24  */
25 public class MutabilityControl {
26     /** whether this instance is mutable */
27     private boolean mutable;
28 
29     /**
30      * Constructs an instance. It is initially mutable.
31      */
MutabilityControl()32     public MutabilityControl() {
33         mutable = true;
34     }
35 
36     /**
37      * Constructs an instance, explicitly indicating the mutability.
38      *
39      * @param mutable {@code true} iff this instance is mutable
40      */
MutabilityControl(boolean mutable)41     public MutabilityControl(boolean mutable) {
42         this.mutable = mutable;
43     }
44 
45     /**
46      * Makes this instance immutable.
47      */
setImmutable()48     public void setImmutable() {
49         mutable = false;
50     }
51 
52     /**
53      * Checks to see whether or not this instance is immutable. This is the
54      * same as calling {@code !isMutable()}.
55      *
56      * @return {@code true} iff this instance is immutable
57      */
isImmutable()58     public final boolean isImmutable() {
59         return !mutable;
60     }
61 
62     /**
63      * Checks to see whether or not this instance is mutable.
64      *
65      * @return {@code true} iff this instance is mutable
66      */
isMutable()67     public final boolean isMutable() {
68         return mutable;
69     }
70 
71     /**
72      * Throws {@link MutabilityException} if this instance is
73      * immutable.
74      */
throwIfImmutable()75     public final void throwIfImmutable() {
76         if (!mutable) {
77             throw new MutabilityException("immutable instance");
78         }
79     }
80 
81     /**
82      * Throws {@link MutabilityException} if this instance is mutable.
83      */
throwIfMutable()84     public final void throwIfMutable() {
85         if (mutable) {
86             throw new MutabilityException("mutable instance");
87         }
88     }
89 }
90