== Why is this an issue?

The `Reader.read()` and the `BufferedReader.readLine()` are used for reading data from a data source.
The return value of these methods is the data read from the data source, or `null` when the end of the data source is reached.
If the return value is ignored, the data read from the source is thrown away and may indicate a bug.

This rule raises an issue when the return values of `Reader.read()` and `BufferedReader.readLine()`
and their subclasses are ignored or merely null-checked.

=== Noncompliant code example

[source,java,diff-id=1,diff-type=noncompliant]
----
public void doSomethingWithFile(String fileName) {
  try(BufferedReader buffReader = new BufferedReader(new FileReader(fileName))) {
    while (buffReader.readLine() != null) { // Noncompliant
      // ...
    }
  } catch (IOException e) {
    // ...
  }
}
----

=== Compliant solution

[source,java,diff-id=1,diff-type=compliant]
----
public void doSomethingWithFile(String fileName) {
  try(BufferedReader buffReader = new BufferedReader(new FileReader(fileName))) {
    String line = null;
    while ((line = buffReader.readLine()) != null) {
      // ...
    }
  } catch (IOException e) {
    // ...
  }
}
----

== Resources

* https://docs.oracle.com/en/java/javase/20/docs/api/java.base/java/io/Reader.html#read()[Oracle SDK 20 - Reader.read()]

* https://docs.oracle.com/en/java/javase/20/docs/api/java.base/java/io/BufferedReader.html#readLine()[Oracle SDK 20 - BufferedReader.readLine()]

ifdef::env-github,rspecator-view[]

'''
== Implementation Specification
(visible only on this page)

=== Message

Use or store the value returned from "xxx" instead of throwing it away.


'''
== Comments And Links
(visible only on this page)

=== is related to: S2674

=== relates to: S899

endif::env-github,rspecator-view[]