BE THE CODER > Tools and Libs > Google Guava Examples > Collections

Google Guava is a java library with lot of utilities and reusable components. This requires the library guava-10.0.jar to be in classpath. The following example shows using Ordering.from() and Ordering.compound() APIs. It allows us to perform multi level ordering.

File Name :	com/bethecoder/tutorials/guava/collection_tests/OrderingMultiLevelTest.java
Author :	Sudhakar KV
Email :	[email protected]


package com.bethecoder.tutorials.guava.collection_tests;



import java.util.Comparator;

import java.util.List;



import com.bethecoder.tutorials.guava.common.Bug;

import com.google.common.collect.Lists;

import com.google.common.collect.Ordering;

import com.google.common.primitives.Ints;



public class OrderingMultiLevelTest {



  /**

   * @param args

   */

  public static void main(String[] args) {



    List<Bug> bugs = Lists.newArrayList(

      new Bug("Bug1", "Open", 3),

      new Bug("Bug2", "Resolved", 3),

      new Bug("Bug3", "Closed", 1),

      new Bug("Bug4", "Open", 4),

      new Bug("Bug5", "Resolved", 2),

      new Bug("Bug6", "Open", 1),

      new Bug("Bug7", "Closed", 3),

      new Bug("Bug8", "Resolved", 1)

    );

    

    Comparator<Bug> statusComp = new Comparator<Bug>() {

      @Override

      public int compare(Bug b1, Bug b2) {

        return b1.getStatus().compareToIgnoreCase(b2.getStatus());

      }

    };



    Comparator<Bug> priorityComp = new Comparator<Bug>() {

      @Override

      public int compare(Bug b1, Bug b2) {

        return Ints.compare(b1.getPriority(), b2.getPriority());

      }

    };

    

    System.out.println("Actual Bug List : ");

    showBugList(bugs);

    

    //Order by status and then priority

    List<Bug> sortedBugs = Ordering.from(statusComp).compound(priorityComp).sortedCopy(bugs);

    System.out.println("\nSorted Bug List : ");

    showBugList(sortedBugs);

  }



  private static void showBugList(List<Bug> bugs) {

    for (Bug bug : bugs) {

      System.out.println(bug);

    }

  }

}

Multilevel Ordering