io.sphere.internal.util.ListUtil Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of sphere-java-client Show documentation

sphere-java-client

There is a newer version: 0.72.1

package io.sphere.internal.util;

import com.google.common.collect.FluentIterable;
import com.google.common.collect.ImmutableList;
import io.sphere.internal.util.SearchUtil;

import java.util.List;
import java.util.Random;

public class ListUtil {
    /** Helper for vararg methods with at least one argument. */
    public static  ImmutableList list(T t, T... ts) {
        ImmutableList.Builder builder = ImmutableList.builder();
        if (t != null) builder = builder.add(t);
        for (T elem: ts) {
            if (elem != null) builder.add(elem);
        }
        return builder.build();
    }

    /** Creates an copy immutable copy of given collection with given element prepended. */
    public static  ImmutableList list(T t, Iterable elems) {
        ImmutableList.Builder builder = ImmutableList.builder();
        if (t != null) builder = builder.add(t);
        for (T e: elems) {
            if (e != null) builder.add(e);
        }
        return builder.build();
    }

    /** Creates an copy immutable copy of given collection with given element prepended. */
    public static  ImmutableList list(Iterable elems1, Iterable elems2) {
        ImmutableList.Builder builder = ImmutableList.builder();
        for (T e: elems1) {
            if (e != null) builder.add(e);
        }
        for (T e: elems2) {
            if (e != null) builder.add(e);
        }
        return builder.build();
    }

    /** Converts a Collection to a List. */
    public static  ImmutableList toList(Iterable elems) {
        if (elems == null) {
            return ImmutableList.of();
        }
        if (elems instanceof ImmutableList) {
            return (ImmutableList)elems;
        }
        return ImmutableList.copyOf(FluentIterable.from(elems).filter(Util.isNotNull));
    }

    private static final ThreadLocal random = new ThreadLocal() {
        @Override protected Random initialValue() {
            return new Random();
        }
    };
    /** Selects a random element from a list. */
    public static  T randomElement(List list) {
        if (list.isEmpty()) throw new IllegalArgumentException("Can't select random element from an empty list.");
        return list.get(random.get().nextInt(list.size()));
    }
}