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Add Ensure Resources Always Get Closed as a Java TIL

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jbranchaud
2024-10-14 16:04:07 -05:00
parent 028b76ba6b
commit 567637497c
2 changed files with 57 additions and 1 deletions

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# Ensure Resources Always Get Closed
Java has a construct known as _try-with-resource_ that allows us to always
ensure opened resources get closed. This is safer than similar cleanup in the
`finally` block which could still leave a memory leak if an error occurs in
that block.
To use the _try-with-resource_ construct, instantiate your opened resource in
parentheses with the `try`.
```java
try (BufferedReader reader = new BufferedReader(new FileReader(filename))) {
// ...
}
```
The resource will be automatically closed when the try/catch block completes.
Here is a full example:
```java
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
public class FileReaderExample {
public static void main(String[] args) {
String fileName = "example.txt";
try (BufferedReader reader = new BufferedReader(new FileReader(fileName))) {
String line;
int lineCount = 0;
while ((line = reader.readLine()) != null && lineCount < 5) {
System.out.println(line);
lineCount++;
}
} catch (IOException e) {
System.out.println("An error occurred while reading the file: " + e.getMessage());
}
}
}
```
You can even specify multiple resources in one `try`. The above does that, but
this will make it more obvious:
```java
try (FileReader fr = new FileReader(filename);
BufferedReader br = new BufferedReader(fr)) {
// ...
}
```
[source](https://docs.oracle.com/javase/tutorial/essential/exceptions/tryResourceClose.html)