ASimpleMap.java

// HUK-SimpleMap/ASimpleMap.java
 
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;

public class ASimpleMap {
    public static void main(String[] args) {
        Map<String,Integer> map = new TreeMap<>();
        map.put("Sue",167);
        map.put("Ann",173);
        map.put("Lea",170);
        map.put("Kim",173);

        Iterator<String> iter = map.keySet().iterator();
        while (iter.hasNext()) {
            String key = iter.next();
            int    val = map.get(key); // auto(un)boxing
            System.out.print(key + ": " + val + "  ");
            if (val == 170) iter.remove();
        }

        System.out.print("\nWe can print a map: " + map);

          // returns null, or the value if present
        map.putIfAbsent("Lea",169);
          // returns old value or null if not present
        map.replace("Lea",170);

        System.out.print("\nIs there a key 'Lea'? " +
                              map.containsKey("Lea"));
        System.out.print("\nIs there a key 'Zoe'? " +
                              map.containsKey("Zoe"));
          // inefficient!
        System.out.println("\nIs any girl 170 cm tall? " +
                                   map.containsValue(170));

        Integer was = map.remove("Ann");
        if (was != null)
            System.out.println("Ann removed, she was " +
                was + " cm tall");
        was = map.remove("Zoe");
        if (was == null)
            System.out.println("There was no 'Zoe'!");

        System.out.println("getOrDefault: 'Zoe'->" +
                         map.getOrDefault("Zoe",-1));
        System.out.println("getOrDefault: 'Lea'->" +
                         map.getOrDefault("Lea",-1));

        System.out.print("Iterating over 'keySet': ");
        for (String s : map.keySet())
            System.out.print(s + "->" + map.get(s) +"  ");

        System.out.print("\nMore efficient way: ");
        for (Map.Entry<String,Integer> e : map.entrySet())
            System.out.print(e.getKey() + "->" +
                             e.getValue() + "  ");
        System.out.println();
    }
}