java-sorting-object-array.java

/**
* http://www.mkyong.com/java/java-object-sorting-example-comparable-and-comparator/
*/

//1. Sort an Array
String[] fruits = new String[] {"Pineapple","Apple", "Orange", "Banana"}; 
Arrays.sort(fruits);
int i=0;
for(String temp: fruits){
	System.out.println("fruits " + ++i + " : " + temp);
}
  
//2. Sort an ArrayList
List<String> fruits = new ArrayList<String>();
fruits.add("Pineapple");
fruits.add("Apple");
fruits.add("Orange");
fruits.add("Banana");
Collections.sort(fruits);
int i=0;
for(String temp: fruits){
	System.out.println("fruits " + ++i + " : " + temp);
}

//3. Sort an Object with Comparable
public class Fruit implements Comparable<Fruit>
  private String fruitName;
	private String fruitDesc;
	private int quantity;
  public int compareTo(Fruit compareFruit) {
  	int compareQuantity = ((Fruit) compareFruit).getQuantity(); 
		//ascending order
		return this.quantity - compareQuantity;
		//descending order
		//return compareQuantity - this.quantity;
	}
}

public class SortFruitObject{
  public static void main(String args[]){
    List<Fruit> fruits = new ArrayList<Fruit>();
    Collections.sort(fruits);
		int i=0;
		for(Fruit temp: fruits){
		   System.out.println("fruits " + ++i + " : " + temp.getFruitName() + 
			", Quantity : " + temp.getQuantity());
		}
	}	
}

//4. Sort an Object with Comparator
//How about sorting with Fruit’s “fruitName” or “Quantity”? The Comparable interface is only allow to 
//sort a single property. To sort with multiple properties, you need Comparator
//See the new updated Fruit class again

public class Fruit implements Comparable<Fruit>{
 
  private String fruitName;
	private String fruitDesc;
	private int quantity;
  
  public int compareTo(Fruit compareFruit) {
  	int compareQuantity = ((Fruit) compareFruit).getQuantity(); 
		//ascending order
		return this.quantity - compareQuantity;
		//descending order
		//return compareQuantity - this.quantity;
	}
 
	public static Comparator<Fruit> FruitNameComparator 
                          = new Comparator<Fruit>() {
	    public int compare(Fruit fruit1, Fruit fruit2) {
	      String fruitName1 = fruit1.getFruitName().toUpperCase();
	      String fruitName2 = fruit2.getFruitName().toUpperCase();
	      //ascending order
	      return fruitName1.compareTo(fruitName2);
	      //descending order
	      //return fruitName2.compareTo(fruitName1);
	    }
	};
}

public static void main(String[] arg){
  Arrays.sort(fruits, Fruit.FruitNameComparator);
}