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Thread: convert arraylist to a hash map

  1. #1
    Junior Member
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    Default convert arraylist to a hash map

    hey guyz how do you change all of these methods when you are replacing the arraylist with a hash map
     public Order() {
            this.orderNumber = orderNumberCounter;
            orderNumberCounter++;
            orderLines = new ArrayList<OrderLine>();
            orderTime = Calendar.getInstance();
        }
     
        /**
         * Constructs a new Order object with the value of the passed in parameters
         * 
         * @param orderLines - the initial value of each order line that is in this order
         */
        public Order(ArrayList<OrderLine> orderLines) {
            this.orderNumber = orderNumberCounter;
            orderNumberCounter++;
     
            for (OrderLine orderLine : orderLines) {
                this.orderLines.add(orderLine);
            }
     
            this.orderTime = Calendar.getInstance();
        }
     
        /**
         * Return the food numbers of foods that are in this order
         * 
         * @return a copy of attribute foodNumbers
         */
        public ArrayList<OrderLine> getOrderLines() {
            return (ArrayList<OrderLine>)orderLines.clone();
        }
     
        /**
         * Add a food to the order along with the correponding quantity
         * 
         * @param food - the food to add 
         * @param quantity - the quantity of the food
         * @return true if the food item is added successfully, false otherwise
         */
        public boolean addItem(Food food, int quantity) {
            if (!orderLines.contains(searchOrderLine(food))) {
                return this.orderLines.add(new OrderLine(food, quantity));
            }
            return false;
        }
     
        /**
         * Add an order line to the order
         * 
         * @param orderLine - the new order line to add in 
         * @return true if the orderLine is added successfully, false otherwise
         */
        public boolean addItem(OrderLine orderLine) {
            if (!orderLines.contains(searchOrderLine(orderLine.getFood()))) {
                return this.orderLines.add(orderLine);
            }
            return false;
        }
     
         /**
         * Remove a food from the order
         * 
          * @param food - the food to remove
          * @return true if the food item is removed successfully, false otherwise
         */
        public boolean removeItem(Food food) {
            return this.orderLines.remove(searchOrderLine(food));
        }
     
        /**
         * Search whether a food already existed in the order
         * 
         * @param food - the food to search
         * @return the order line containing the food 
         */
        private OrderLine searchOrderLine(Food food) {
            for (OrderLine orderLine : orderLines) {
                if (orderLine.getFood().getFoodNumber() == food.getFoodNumber()) {
                    return orderLine;
                }
            }
            return new OrderLine();
        }

    tahnx in advance


  2. #2
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    Thumbs up Re: convert arraylist to a hash map

    package mahesh.core.util.vo;
     
    import java.io.Serializable;
     
    public class Dimension implements Serializable {
     
        private long x,y;
     
        public Dimension(){}
     
        public Dimension(long x, long y) {
            super();
            this.x = x;
            this.y = y;
        }
     
        public long getX() {
            return x;
        }
     
        public void setX(long x) {
            this.x = x;
        }
     
        public long getY() {
            return y;
        }
     
        public void setY(long y) {
            this.y = y;
        }
     
        public String toString(){
            return x + " " + y;
        }
    }

    package mahesh.core.util;
     
    import mahesh.core.util.vo.Dimension;
     
    import java.util.ArrayList;
    import java.util.List;
    import java.util.Map;
    import java.util.HashMap;
    import java.lang.reflect.Method;
    import java.lang.reflect.InvocationTargetException;
     
    /**
     * @author Maheshkumarp
     * @version 1.0
     *          Date: Jul 29, 2009 - Time: 10:05:22 AM
     */
    public class ListUtils<K> {
     
        public static String camelHump(String str) {
            if(str != null && (str = str.trim()).length() > 0) {
                str = str.substring(0, 1).toUpperCase() + str.substring(1);
            }
            return str;
        }
     
        public static String convertFieldToAccessor(String filed) {
            return "get" + camelHump(filed);
        }
     
        public <V> Map<K, V> toMap(List<V> list, String keyField) throws NoSuchMethodException, InvocationTargetException, IllegalAccessException {
            String accessor = convertFieldToAccessor(keyField);
            Map<K, V> map = new HashMap<K, V>();
            for(V obj : list) {
                Method method = obj.getClass().getDeclaredMethod(accessor);
                K key = (K)method.invoke(obj);
                map.put(key, obj);
            }
            return map;
        }
     
        public static void main(String[] args) throws Exception {
            List<Dimension> dimensionList = new ArrayList<Dimension>();
            dimensionList.add(new Dimension(1, 2));
            dimensionList.add(new Dimension(2, 2));
            dimensionList.add(new Dimension(3, 223));
            dimensionList.add(new Dimension(4, 2));
            Map<Long, Dimension> dimensionMap = new ListUtils<Long>().toMap(dimensionList, "x");
            System.out.println(dimensionMap);
        }
    }

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