Main.java Source code

Introduction

Here is the source code for Main.java

Source

//package com.java2s;
import java.util.*;

public class Main {

    public static <T, C extends Collection<T>> C getElements(C c, int offset, int size) {
        if (c == null) {
            return null;

        } else if (c.isEmpty() || offset >= c.size() || size <= 0) {
            return newCollection(c);
        }

        if (offset < 0) {
            offset = Math.max(0, c.size() + offset);
        }

        if (offset + size > c.size()) {
            size = c.size() - offset;
        }

        C result = newCollection(c);
        if (c instanceof List) {
            result.addAll(((List<T>) c).subList(offset, offset + size));

        } else {
            for (int i = offset; i < offset + size; i++) {
                result.add(getElement(c, i));
            }
        }

        return result;
    }

    public static boolean isEmpty(Collection<?> collection) {
        return (collection == null || collection.isEmpty());
    }

    public static int size(Collection<?> collection) {
        return (collection == null ? 0 : collection.size());
    }

    public static int size(Collection<?>... collections) {
        int size = 0;
        if (collections != null) {
            for (Collection<?> c : collections) {
                if (c != null) {
                    size += c.size();
                }
            }
        }

        return size;
    }

    @SuppressWarnings("unchecked")
    public static <C extends Collection<?>> C newCollection(Object reference) {
        Class<?> clazz = null;
        if (reference instanceof Collection<?>) {
            clazz = (Class<?>) reference.getClass();

        } else if (reference instanceof Class<?> && Collection.class.isAssignableFrom((Class<?>) reference)) {
            clazz = (Class<?>) reference;

            if (clazz.equals(List.class)) {
                clazz = (Class<?>) ArrayList.class;

            } else if (clazz.equals(Set.class)) {
                clazz = (Class<?>) LinkedHashSet.class;
            }
        }

        if (clazz != null) {
            try {
                return (C) clazz.newInstance();
            } catch (Exception e) {
            }
        }

        return null;
    }

    public static <T> T getElement(Collection<T> c, int index) {
        return getElement(c, index, null);
    }

    public static <T> T getElement(Collection<T> c, int index, T defElement) {
        if (isEmpty(c) || index >= c.size()) {
            return defElement;
        }

        if (index < 0) {
            index = c.size() + index;
            if (index < 0) {
                return defElement;
            }
        }

        if (c instanceof List) {
            return ((List<T>) c).get(index);

        } else {
            for (T element : c) {
                if (index-- == 0) {
                    return element;
                }
            }

            // unreachable
            return defElement;
        }
    }
}