Use try-with-resources instead of manual resource management

Medium

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JavaClean code

What is it?

This practice is activated when code manually opens and closes resources such as files, network connections, or database connections without using the try-with-resources statement introduced in Java 7.

Why apply it?

Ensuring proper closure and cleanup of resources is critical to preventing memory leaks and resource contention, and the try-with-resources statement automates this process, making the code more robust and less error-prone.

How to fix it?

Replace manual try-catch-finally blocks for resource management with the try-with-resources statement to automatically handle resource closing.

Read more:

https://docs.oracle.com/javase/tutorial/essential/exceptions/tryResourceClose.html

Examples

Example 1:

Positive

Correct implementation following the practice.

package org.example;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

public final class Util {

    public static Map<String, Integer> nameCount(List<String> names) {
        return names.stream()
                .collect(Collectors.toMap(name -> name, name -> 1, Integer::sum));

    }

    public static void printNames(List<String> names) {
        names.forEach(System.out::println);
    }

    public static Integer sum(List<Integer> numbers) {
        return numbers.stream()
                .reduce(0, Integer::sum);
    }

    public static int increment(int value) {
        return value + 1;
    }

    public static void readFile(String fileName) throws FileNotFoundException {
        try (InputStream input = new FileInputStream(fileName)) {
            // Read file
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Negative

Incorrect implementation that violates the practice.

package org.example;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

public final class Util {

    public static Map<String, Integer> nameCount(List<String> names) {
        return names.stream()
                .collect(Collectors.toMap(name -> name, name -> 1, Integer::sum));

    }

    public static void printNames(List<String> names) {
        names.forEach(System.out::println);
    }

    public static Integer sum(List<Integer> numbers) {
        return numbers.stream()
                .reduce(0, Integer::sum);
    }

    public static int increment(int value) {
        return value + 1;
    }

    public static void readFile(String fileName) throws FileNotFoundException {
        InputStream input = null;
        try {
            input = new FileInputStream("file.txt");
            // Read file
        } finally {
            if (input != null) {
                try {
                    input.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}