Initial attempt at #92

common/src/main/java/com/lishid/openinv/util/Cache.java

@@ -19,11 +19,11 @@ package com.lishid.openinv.util;
 import com.google.common.collect.Multimap;
 import com.google.common.collect.TreeMultimap;
 import java.util.ArrayList;
-import java.util.Comparator;
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 
 /**
  * A minimal thread-safe time-based cache implementation backed by a HashMap and TreeMultimap.
@@ -45,20 +45,9 @@ public class Cache<K, V> {
      * @param postRemoval Function used to perform any operations required when a key is invalidated
      */
     public Cache(final long retention, final Function<V> inUseCheck, final Function<V> postRemoval) {
-        this.internal = new HashMap<K, V>();
+        this.internal = new HashMap<>();
 
-        this.expiry = TreeMultimap.create(new Comparator<Long>() {
-                    @Override
-                    public int compare(final Long long1, final Long long2) {
-                        return long1.compareTo(long2);
-                    }
-                },
-                new Comparator<K>() {
-                    @Override
-                    public int compare(final K k1, final K k2) {
-                        return k1 == k2 || k1 != null && k1.equals(k2) ? 0 : 1;
-                    }
-                });
+        this.expiry = TreeMultimap.create(Long::compareTo, (k1, k2) -> Objects.equals(k1, k2) ? 0 : 1);
 
         this.retention = retention;
         this.inUseCheck = inUseCheck;
@@ -160,7 +149,7 @@ public class Cache<K, V> {
     private void lazyCheck() {
         long now = System.currentTimeMillis();
         synchronized (this.internal) {
-            List<K> inUse = new ArrayList<K>();
+            List<K> inUse = new ArrayList<>();
             for (Iterator<Map.Entry<Long, K>> iterator = this.expiry.entries().iterator(); iterator
                     .hasNext();) {
                 Map.Entry<Long, K> entry = iterator.next();

common/src/main/java/com/lishid/openinv/util/Pair.java

@@ -0,0 +1,53 @@
+/*
+ * Copyright (C) 2011-2019 lishid. All rights reserved.
+ *
+ * This program 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, version 3.
+ *
+ * This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package com.lishid.openinv.util;
+
+/**
+ * Simple tuple.
+ *
+ * @param <L> the left value
+ * @param <R> the right value
+ *
+ * @author Jikoo
+ */
+public class Pair<L, R> {
+
+    private L left;
+    private R right;
+
+    public Pair(L left, R right) {
+        this.left = left;
+        this.right = right;
+    }
+
+    public L getLeft() {
+        return left;
+    }
+
+    public void setLeft(L left) {
+        this.left = left;
+    }
+
+    public R getRight() {
+        return right;
+    }
+
+    public void setRight(R right) {
+        this.right = right;
+    }
+
+}

common/src/main/java/com/lishid/openinv/util/SingleFieldList.java

@@ -0,0 +1,201 @@
+/*
+ * Copyright (C) 2011-2019 lishid. All rights reserved.
+ *
+ * This program 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, version 3.
+ *
+ * This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package com.lishid.openinv.util;
+
+import java.util.AbstractCollection;
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.List;
+import java.util.ListIterator;
+import java.util.NoSuchElementException;
+import java.util.Objects;
+import java.util.function.Consumer;
+import java.util.function.Supplier;
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * A List implementation intended for wrapping a single field.
+ *
+ * @param <V> the type of the field
+ *
+ * @author Jikoo
+ */
+public class SingleFieldList<V> extends AbstractCollection<V> implements List<V> {
+
+    private final Supplier<V> fieldGetter;
+    private final Consumer<V> fieldSetter;
+
+    public SingleFieldList(@NotNull Supplier<V> fieldGetter, @NotNull Consumer<V> fieldSetter) {
+        this.fieldGetter = fieldGetter;
+        this.fieldSetter = fieldSetter;
+    }
+
+    @Override
+    public int size() {
+        return 1;
+    }
+
+    @Override
+    public boolean contains(Object o) {
+        return Objects.equals(o, fieldGetter.get());
+    }
+
+    @NotNull
+    @Override
+    public Iterator<V> iterator() {
+        return listIterator();
+    }
+
+    @Override
+    public boolean addAll(int index, @NotNull Collection<? extends V> c) {
+        return super.addAll(c);
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        return o instanceof SingleFieldList
+                && fieldGetter.equals(((SingleFieldList) o).fieldGetter)
+                && fieldSetter.equals(((SingleFieldList) o).fieldSetter);
+    }
+
+    @Override
+    public int hashCode() {
+        return fieldSetter.hashCode() * 17 * fieldGetter.hashCode();
+    }
+
+    @Override
+    public V get(int index) {
+        if (index != 0) {
+            throw new IndexOutOfBoundsException();
+        }
+        return fieldGetter.get();
+    }
+
+    @Override
+    public V set(int index, V element) {
+        if (index != 0) {
+            throw new IndexOutOfBoundsException();
+        }
+
+        V old = fieldGetter.get();
+        fieldSetter.accept(element);
+
+        return old;
+    }
+
+    @Override
+    public void add(int index, V element) {
+        throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public V remove(int index) {
+        throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public int indexOf(Object o) {
+        return fieldGetter.get().equals(o) ? 0 : -1;
+    }
+
+    @Override
+    public int lastIndexOf(Object o) {
+        return indexOf(o);
+    }
+
+    @NotNull
+    @Override
+    public ListIterator<V> listIterator() {
+        return new ListIterator<V>() {
+            private boolean hasNext = true;
+
+            @Override
+            public boolean hasNext() {
+                return hasNext;
+            }
+
+            @Override
+            public V next() {
+                if (!hasNext) {
+                    throw new NoSuchElementException();
+                }
+                return fieldGetter.get();
+            }
+
+            @Override
+            public boolean hasPrevious() {
+                return !hasNext;
+            }
+
+            @Override
+            public V previous() {
+                if (hasNext) {
+                    throw new NoSuchElementException();
+                }
+                return fieldGetter.get();
+            }
+
+            @Override
+            public int nextIndex() {
+                return hasNext ? 0 : 1;
+            }
+
+            @Override
+            public int previousIndex() {
+                return hasNext ? -1 : 0;
+            }
+
+            @Override
+            public void remove() {
+                throw new UnsupportedOperationException();
+            }
+
+            @Override
+            public void set(V v) {
+                fieldSetter.accept(v);
+            }
+
+            @Override
+            public void add(V v) {
+                throw new UnsupportedOperationException();
+            }
+        };
+    }
+
+    @NotNull
+    @Override
+    public ListIterator<V> listIterator(int index) {
+        if (index != 0) {
+            throw new IndexOutOfBoundsException();
+        }
+        return listIterator();
+    }
+
+    @NotNull
+    @Override
+    public List<V> subList(int fromIndex, int toIndex) {
+        if (fromIndex != 0 || toIndex != 1) {
+            throw new IndexOutOfBoundsException();
+        }
+
+        return this;
+    }
+
+    @Override
+    public void clear() {}
+
+}