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package net.dongliu.commons.lang.collection;

import java.util.Arrays;
import java.util.Collections;
import java.util.List;

/**
 * utils method for list
 *
 * @author Dong Liu
 */
public class Lists {

    /**
     * get a list backend by Array.
     * 
     * {@code List list = Lists.of("test", "test2");}
     * 
     */
    @SafeVarargs
    public static  List of(T... values) {
        return Arrays.asList(values);
    }

    /**
     * get immutable list
     * 
     * {@code List list = Lists.immutable("test", "test2");}
     * 
     */
    @SafeVarargs
    public static  List immutable(T... values) {
        return Collections.unmodifiableList(of(values));
    }

    /**
     * get immutable list
     */
    public static  List immutable(List list) {
        return Collections.unmodifiableList(list);
    }

    /**
     * get sub list by begin(included) and end(not included) index.
     * begin and end can be negative, will be eval as list.size() + begin/end.
     * {@code
     *     List list = Lists.of(1, 5, 9, 10);
     *     Lists.sub(list, 1, 3) returns Lists.of(5, 9);
     *     Lists.sub(list, 1, -1) returns Lists.of(5, 9);
     *     Lists.sub(list, 1, 100) returns Lists.of(5, 9, 10);
     *     Lists.sub(list, -100, 100) returns Lists.of(1, 5, 9, 10);
     *     Lists.sub(list, 5, 0) returns empty list;
     *     Lists.sub(null, 5, 0) returns null;
     *     }
     * 
     *
     * @param list can be null. when list is null, always return null
     * @return sub list
     */
    public static  List sub(List list, int begin, int end) {
        if (list == null) {
            return null;
        }
        int len = list.size();
        if (begin < 0) {
            begin += len;
        }
        if (end < 0) {
            end += len;
        }
        begin = Math.max(begin, 0);
        begin = Math.min(begin, len);
        end = Math.max(begin, end);
        end = Math.min(end, len);
        return list.subList(begin, end);
    }

    /**
     * get sub list by begin(included) index, till the end of list.
     * begin can be negative, will be eval as list.size() + begin.
     * {@code
     *     List list = Lists.of(1, 5, 9, 10);
     *     Lists.sub(list, 1) --> Lists.of(5, 9, 10);
     *     Lists.sub(list, -1) --> Lists.of(10);
     *     Lists.sub(list, -100) --> Lists.of(1, 5, 9, 10);
     *     Lists.sub(null, -2) returns null;
     *     }
     * 
     *
     * @param list can be null. when list is null, always return null
     * @return subString
     * @throws ArrayIndexOutOfBoundsException
     */
    public static  List sub(List list, int begin) {
        return sub(list, begin, list.size());
    }
}