Import necessary nms and fix decompile errors

sources/src/main/java/net/minecraft/server/RegistryID.java

@@ -0,0 +1,148 @@
+package net.minecraft.server;
+
+import com.google.common.base.Predicates;
+import com.google.common.collect.Iterators;
+import java.util.Iterator;
+import javax.annotation.Nullable;
+
+public class RegistryID<K> implements Registry {
+
+    private static final Object a = null;
+    private K[] b;
+    private int[] c;
+    private K[] d;
+    private int e;
+    private int f;
+
+    public RegistryID(int i) {
+        i = (int) ((float) i / 0.8F);
+        this.b = (K[]) (new Object[i]);
+        this.c = new int[i];
+        this.d = (K[]) (new Object[i]);
+    }
+
+    public int getId(@Nullable K k0) {
+        return this.c(this.b(k0, this.d(k0)));
+    }
+
+    @Nullable
+    public K fromId(int i) {
+        return i >= 0 && i < this.d.length ? this.d[i] : null;
+    }
+
+    private int c(int i) {
+        return i == -1 ? -1 : this.c[i];
+    }
+
+    public int c(K k0) {
+        int i = this.c();
+
+        this.a(k0, i);
+        return i;
+    }
+
+    private int c() {
+        while (this.e < this.d.length && this.d[this.e] != null) {
+            ++this.e;
+        }
+
+        return this.e;
+    }
+
+    private void d(int i) {
+        K[] aobject = this.b;
+        int[] aint = this.c;
+
+        this.b = (K[]) (new Object[i]);
+        this.c = new int[i];
+        this.d = (K[]) (new Object[i]);
+        this.e = 0;
+        this.f = 0;
+
+        for (int j = 0; j < aobject.length; ++j) {
+            if (aobject[j] != null) {
+                this.a(aobject[j], aint[j]);
+            }
+        }
+
+    }
+
+    public void a(K k0, int i) {
+        int j = Math.max(i, this.f + 1);
+        int k;
+
+        if ((float) j >= (float) this.b.length * 0.8F) {
+            for (k = this.b.length << 1; k < i; k <<= 1) {
+                ;
+            }
+
+            this.d(k);
+        }
+
+        k = this.e(this.d(k0));
+        this.b[k] = k0;
+        this.c[k] = i;
+        this.d[i] = k0;
+        ++this.f;
+        if (i == this.e) {
+            ++this.e;
+        }
+
+    }
+
+    private int d(@Nullable K k0) {
+        return (MathHelper.f(System.identityHashCode(k0)) & Integer.MAX_VALUE) % this.b.length;
+    }
+
+    private int b(@Nullable K k0, int i) {
+        int j;
+
+        for (j = i; j < this.b.length; ++j) {
+            if (this.b[j] == k0) {
+                return j;
+            }
+
+            if (this.b[j] == RegistryID.a) {
+                return -1;
+            }
+        }
+
+        for (j = 0; j < i; ++j) {
+            if (this.b[j] == k0) {
+                return j;
+            }
+
+            if (this.b[j] == RegistryID.a) {
+                return -1;
+            }
+        }
+
+        return -1;
+    }
+
+    private int e(int i) {
+        int j;
+
+        for (j = i; j < this.b.length; ++j) {
+            if (this.b[j] == RegistryID.a) {
+                return j;
+            }
+        }
+
+        for (j = 0; j < i; ++j) {
+            if (this.b[j] == RegistryID.a) {
+                return j;
+            }
+        }
+
+        throw new RuntimeException("Overflowed :(");
+    }
+
+    public Iterator<K> iterator() {
+        return Iterators.filter(Iterators.forArray(this.d), Predicates.notNull());
+    }
+
+    public int b() {
+        return this.f;
+    }
+}