Local variable type inference in Java 10: How to use var keyword in try-with-resources statement

Local variable type inference in Java 10: How to use var keyword in try-with-resources statement

Introduction:
Java 10 has some improvements in local variable type inference. The introduction of the var keyword allows developers to omit the type when declaring variables and let the compiler infer it. This article will focus on using the var keyword in try-with-resources statements.

1. What is the try-with-resources statement?
In the try-with-resources statement introduced in Java 7, we can automatically manage resources. Regardless of whether an exception occurs, the try-with-resources statement automatically closes resources after using them. The following is the general form of using try-with-resources:

try (ResourceType resource = new ResourceType()) {
    // 使用资源
} catch (Exception e) {
    // 处理异常
}

2. Local variable type inference in Java 10
Before Java 10, we need to explicitly use try-with-resources statement Declares the type of resource. For example:

try (BufferedReader reader = new BufferedReader(new FileReader("file.txt"))) {
    // 使用资源
} catch (Exception e) {
    // 处理异常
}

In Java 10, we can use local variable type inference and use the var keyword to let the compiler automatically infer the type of resources:

try (var reader = new BufferedReader(new FileReader("file.txt"))) {
    // 使用资源
} catch (Exception e) {
    // 处理异常
}

With the var keyword, we can Declare resources more concisely and reduce code duplication.

3. Precautions after using var
Although using the var keyword can make the code more concise, you still need to pay attention to some details when using it.

1. var can only be used for the declaration of local variables, but not for fields, method parameters, return types, etc.
2. var The variable declared must have an initial value.
3. The inferred variable type is determined based on the type of the initialization expression, and null cannot be used for initialization during declaration.

4. Benefits of local variable type inference
Using local variable type inference brings some benefits, as follows:

1. Simplicity: by omitting the type , reducing code redundancy and making the code more concise.
2. Readability: Reduces the interference of variable types, making the code more readable.
3. Maintainability: When changing the code, there is no need to modify the type of the variable, only the variable initialization expression, which reduces the possibility of errors.

Conclusion:
In Java 10, local variable type inference allows developers to declare local variables more conveniently by introducing the var keyword, especially in the try-with-resources statement. . By using the var keyword, you can make the code more concise and improve the readability and maintainability of the code.

Reference code example:

import java.io.BufferedReader;
import java.io.FileReader;

public class Example {
    public static void main(String[] args) {
        try (var reader = new BufferedReader(new FileReader("file.txt"))) {
            String line;
            while ((line = reader.readLine()) != null) {
                System.out.println(line);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

The above is an introduction to local variable type inference in Java 10 and how to use the var keyword in the try-with-resources statement. This feature allows us to write more concise, readable and maintainable code. I hope this article helps you better understand and use this feature.

The above is the detailed content of Local variable type inference in Java 10: How to use var keyword in try-with-resources statement. For more information, please follow other related articles on the PHP Chinese website!