Cassandra is an open source distributed database, it combines dynamic key/value and column oriented feature of Bigtable.Features of Cassandra are:Flexible schema, no need to design schema first, it's very convenient to add or delete stringsSupport range search on keysHigh usability, extensible. The single node error will not affect the cluster.We can think Cassandra's data model as a 4 or 5 dimensional Hash.COLUMNColumns is the smallest data unit in Cassandra, it is a 3 dimensional data type including name,value and timestamp. { // This is a column name: "逖靖寒的�...

This is an classical question, the general solution to this question is first using sorting algorithm to sort the array, then get the kth number in the array, the complexity is O(nlogn), we can also use selective sort or head sort to, the complexity of selective sort is O(kn) and heap sort is O(nlogk). The better solution is to use quick sort to find the kth smallest number, the complexity is O(n), the worst case cost is O(n^2). But today we introduce one more solution which has the worst case cost O(n).First let's check the quick sort solution, quick sort is to find one number, then put all n...

Comparable and comparator are two similar interfaces used to compare objects in Java. When we want to sort a list of objects such as Employee or User etc, we may need to implement these interfaces to make them comparable as we want. However, there are some differences between comparable and comparator interface.ComparableA comparable object is capable of comparing itself with another object. The class itself must implements the java.lang.Comparable interface in order to be able to compare its instances.ComparatorA comparator object is capable of comparing two different objects. The class is no...