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// Copyright 2015 The Bazel Authors. All rights reserved.
//
// 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.
package com.google.devtools.build.lib.sandbox;
import com.google.common.collect.ForwardingMap;
import java.util.LinkedHashMap;
import java.util.Map;
/**
* A map that throws an exception when trying to replace a key (i.e. once a key gets a value,
* any additional attempt of putting a value on the same key will throw an exception).
*/
final class MountMap<K, V> extends ForwardingMap<K, V> {
final LinkedHashMap<K, V> delegate = new LinkedHashMap<>();
@Override
protected Map<K, V> delegate() {
return delegate;
}
@Override
public V put(K key, V value) {
V previousValue = get(key);
if (previousValue == null) {
return super.put(key, value);
} else if (previousValue.equals(value)) {
return value;
} else {
throw new IllegalArgumentException(
String.format("Cannot mount both '%s' and '%s' onto '%s'", previousValue, value, key));
}
}
@Override
public void putAll(Map<? extends K, ? extends V> map) {
for (Entry<? extends K, ? extends V> entry : map.entrySet()) {
put(entry.getKey(), entry.getValue());
}
}
}
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