Sorting a list in Java using 2 criteria

Given an object class that looks like this:

public class MyObject {
    public String getString() { ... }
    public Date getDate() { ... }
    ...
}

Write a custom comparator class like so:

public class ObjectComparator implements Comparator{

    public int compare(Object obj1, Object obj2) {
        MyObject myObj1 = (MyObject)obj1;
        MyObject myObj2 = (MyObject)obj2;
        stringResult = myObj1.getString().compareTo(myObj2.getString());
        if (stringResult == 0) {
            // Strings are equal, sort by date
            return myObj1.getDate().compareTo(myObj2.getDate());
        }
        else {
            return stringResult;
        }
    }
}

Then sort as follows:

Collections.sort(objectList, new ObjectComparator());

With Java 8, this is really easy. Given

class MyClass {
    String getString() { ... }
    Date getDate() { ... }
}

You can easily sort a list as follows:

List<MyClass> list = ...
list.sort(Comparator.comparing(MyClass::getString).thenComparing(MyClass::getDate));

Implement a custom Comparator, using a compare(a,b) method like the following:

Plain Java:

 public int compare(YourObject o1, YourObject o2) {
    int result = o1.getProperty1().compareTo(o2.getProperty1()));
    if(result==0) result = o1.getProperty2().compareTo(o2.getProperty2());
    return result;
 }

With Guava (using ComparisonChain):

public int compare(YourObject o1, YourObject o2) {
    return ComparisonChain.start()
      .compare(o1.getProperty1(), o2.getProperty1())
      .compare(o1.getProperty2(), o2.getProperty2())
      .result();
 }

With Commons / Lang (using CompareToBuilder):

public int compare(YourObject o1, YourObject o2) {
    return new CompareToBuilder()
      .append(o1.getProperty1(), o2.getProperty1())
      .append(o1.getProperty2(), o2.getProperty2())
      .toComparison();
 }

(All three versions are equivalent, but the plain Java version is the most verbose and hence most error-prone one. All three solutions assume that both o1.getProperty1() and o1.getProperty2() implement Comparable).

(Taken from this previous answer of mine)

---

now do Collections.sort(yourList, yourComparator)