Now we will put some objects to the HashMap.
First we will create new Car class.
After that you can see how to add some object to these collection in line #39.
In line #46 we are checking if there is key "two" in our HashMap.
In line #49 we are checking if there is value "four" in HashMap.
In line #52 we are checking how much keys there is in our HashMap.
In line #54 you can see how get Object from HashMap by key.
In line #59 we are removing Object by key.
In lines #62 and #68 there is iterating through HashMap by key and
in line #74 there is iterating by value.
package p_2013_04_03; import java.util.HashMap; import java.util.Map; class Car { private String brand; private int year; public Car( String aBrand, int aYear ) { this.brand = aBrand; this.year = aYear; } public void showBrand() { System.out.println( this.brand ); } public void showYear() { System.out.println( this.year ); } } public class MyHashMap { public static void main(String[] args) { HashMaphm = new HashMap (); Car opel = new Car("Opel", 2009); Car ford = new Car("Ford", 2007); Car bmw = new Car("BMW", 2011); Car mercedes = new Car("Mercedes", 2011); // put new value to the Map hm.put("one", opel); hm.put("two", ford); hm.put("three", bmw); hm.put("four", mercedes); // check if Map contains key: true or false System.out.println( hm.containsKey("two") ); // check if Map contains value: true or false System.out.println( hm.containsKey("four") ); // return the number of keys System.out.println( hm.size() ); // get object from the Map by key Car carFromThree = hm.get("three"); carFromThree.showBrand(); // remove object from Map hm.remove("three"); // Iterate through Map - by key for(Map.Entry entry : hm.entrySet()) { System.out.println( "Key: " + entry.getKey() + " | Value : " + entry.getValue() ); } // Iterate through Map - by key for(String key : hm.keySet()) { System.out.println( "Key: " + key ); } // Iterate through Map - by value for(Car car : hm.values()) { System.out.print( "Value: " ); car.showBrand(); } } }
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