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Lightweight analysis tool for detecting mutability in Java classes.

There is a newer version: 0.10.6

package org.mutabilitydetector.checkers;

/*
 * #%L
 * MutabilityDetector
 * %%
 * Copyright (C) 2008 - 2014 Graham Allan
 * %%
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * #L%
 */



import static java.util.Collections.unmodifiableList;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class VarStack {

    private List indices = new ArrayList();
    private List snapshots = new ArrayList();
    private Iterator snapshotsIterator = snapshots.iterator();

    public void visitVarInsn(int var) {
        indices.add(var);
    }

    public void takeSnapshotOfVarsAtPutfield() {
        snapshots.add(new VarStackSnapshot(indices));
        snapshotsIterator = snapshots.iterator();
    }

    public VarStackSnapshot next() {
        return snapshotsIterator.next();
    }

    public static class VarStackSnapshot {

        private final List indices;

        public VarStackSnapshot(List indices) {
            this.indices = unmodifiableList(new ArrayList(indices));
        }

        public boolean thisObjectWasAddedToStack() {
            // the "this" reference is at position 0 of the local variable table
            return indices.contains(0);
        }

        public int indexOfOwningObject() {
            int stackSpaceToLookBack = 1;
            return indices.get((indices.size() - 1) - stackSpaceToLookBack);
        }

    }

}