How to Sort One List Based on the Order of Another List in Java?

Sorting One List Based on Another in Java

In Java, it is possible to sort a list based on another list's order. This can be useful in situations where you have a specific sequence of items in one list (listB) and you want to rearrange a second list (listA) to match that order.

One way to achieve this is by using the Collections.sort() method with a customized Comparator as follows:

<code class="java">Collections.sort(listToSort, new Comparator<T>() {
    @Override
    public int compare(T o1, T o2) {
        return listWithOrder.indexOf(o1) - listWithOrder.indexOf(o2);
    }
});</code>

Here, listToSort represents your unsorted list, and listWithOrder contains the desired order. This Comparator sorts listToSort based on the order of the elements in listWithOrder.

For Java 8 and later, you can simplify the code using lambdas and the comparingInt() method:

<code class="java">listToSort.sort(Comparator.comparingInt(listWithOrder::indexOf));</code>

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