What is Java stream and how to use it

Supakon_k
2 min readDec 6, 2021

Java stream is standard API in Java used to process collection of object.

there are many operation in java stream. I will show you some list of operation with example by the following.

before dive into API, There are two main operation category are

  • Intermediate operation
  • Terminal operation

Intermediate operation

Intermediate operation is used to do some operation after stream method or can chain with another method.

some intermediate operation are

  • map
  • filter
  • sorted

Terminal operation

Terminal operation is used to do some operation on the end of stream can’t chain function after terminal operation.

some terminal operation are

  • collect
  • forEach
  • reduce

Now, I will show to how to use these method

map

map method isused to transform element in collection to another form for example:

filter

filter method is used to filter some element in collection that equal to the logic for example:

sorted

sorted method is used to sort element in collection for example:

collect

collect method is used to collect element back to some type of list for example:

forEach

forEach method is used to iterate element in collection. (in convention do not use forEach to transform element in collection use map instead). For example:

reduce

reduce method is used to turn collection to single value for example:

Summary

There are a lot of method of Java stream, here is Stream (Java Platform SE 8 ) (oracle.com) you can see more method can use in Java stream. Enjoy coding.

reference

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