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Jython is an implementation of the high-level, dynamic, object-oriented language Python written in 100% Pure Java, and seamlessly integrated with the Java platform. It thus allows you to run Python on any Java platform.

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package org.python.util;

import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedHashSet;
import java.util.IdentityHashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

/**
 * Static methods to make instances of collections with their generic types inferred from what
 * they're being assigned to. The idea is stolen from Sets, Lists and
 * Maps from Google
 * Collections.
 */
public class Generic {

    /**
     * Our default ConcurrentHashMap sizes. Only concurreny level differs from
     * ConcurrentHashMap's defaults: it's significantly lower to reduce allocation cost.
     */
    public static final int CHM_INITIAL_CAPACITY = 16;
    public static final float CHM_LOAD_FACTOR = 0.75f;
    public static final int CHM_CONCURRENCY_LEVEL = 2;

    /**
     * Makes a List with its generic type inferred from whatever it's being assigned to.
     */
    public static  List list() {
        return new ArrayList();
    }

    /**
     * Makes a List with its generic type inferred from whatever it's being assigned to.
     * Sets initial capacity accordingly.
     */
    public static  List list(int capacity) {
        return new ArrayList(capacity);
    }

    /**
     * Makes a List with its generic type inferred from whatever it's being assigned to filled with
     * the items in contents.
     */
    @SafeVarargs
    public static  List list(U... contents) {
        List l = new ArrayList(contents.length);
        for (T t : contents) {
            l.add(t);
        }
        return l;
    }

    /**
     * Makes a Map using generic types inferred from whatever this is being assigned to.
     */
    public static  Map map() {
        return new HashMap();
    }

    /**
     * Makes an IdentityHashMap using generic types inferred from whatever this is being
     * assigned to.
     */
    public static  Map identityHashMap() {
        return new IdentityHashMap();
    }

    /**
     * Makes an IdentityHashMap using generic types inferred from whatever this is being
     * assigned to.
     * Sets initial capacity accordingly.
     */
    public static  Map identityHashMap(int capacity) {
        return new IdentityHashMap(capacity);
    }

    /**
     * Makes a ConcurrentMap using generic types inferred from whatever this is being
     * assigned to.
     */
    public static  ConcurrentMap concurrentMap() {
        return new ConcurrentHashMap(CHM_INITIAL_CAPACITY, CHM_LOAD_FACTOR,
                                           CHM_CONCURRENCY_LEVEL);
    }

    /**
     * Makes a Set using the generic type inferred from whatever this is being assigned to.
     */
    public static  Set set() {
        return new HashSet();
    }

    /**
     * Makes a LinkedHashSet using the generic type inferred from whatever this is being assigned to.
     */
    public static  Set linkedHashSet() {
        return new LinkedHashSet();
    }

    /**
     * Makes a LinkedHashSet using the generic type inferred from whatever this is being assigned to.
     * Sets initial capacity accordingly.
     */
    public static  Set linkedHashSet(int capacity) {
        return new LinkedHashSet(capacity);
    }

    /**
     * Makes a Set using the generic type inferred from whatever this is being assigned to filled
     * with the items in contents.
     */
    @SafeVarargs
    public static  Set set(U... contents) {
        Set s = new HashSet(contents.length);
        for (U u : contents) {
            s.add(u);
        }
        return s;
    }

    /**
     * Makes a Set, ensuring safe concurrent operations, using generic types inferred from
     * whatever this is being assigned to.
     */
    public static  Set concurrentSet() {
        return Collections.newSetFromMap(Generic.concurrentMap());
    }

}