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
17package 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 */
25public class MutabilityControl {
26    /** whether this instance is mutable */
27    private boolean mutable;
28
29    /**
30     * Constructs an instance. It is initially mutable.
31     */
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     */
41    public MutabilityControl(boolean mutable) {
42        this.mutable = mutable;
43    }
44
45    /**
46     * Makes this instance immutable.
47     */
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     */
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     */
67    public final boolean isMutable() {
68        return mutable;
69    }
70
71    /**
72     * Throws {@link MutabilityException} if this instance is
73     * immutable.
74     */
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     */
84    public final void throwIfMutable() {
85        if (mutable) {
86            throw new MutabilityException("mutable instance");
87        }
88    }
89}
90