How to read input data in java

Java provides three methods to read input data: Use the Scanner class, use the BufferedReader class, use the DataInputStream class

Use Java Reading input data

Java provides a variety of methods to read input data from users or files, including:

1. Use the Scanner class

• Create a Scanner object, passing in the source from which to read input (such as System.in or a file).
• Use next(), nextInt() and other methods to read different types of data.
• Remember to close the Scanner object to release resources.

Example:

<code class="java">Scanner scanner = new Scanner(System.in);
String input = scanner.nextLine(); // 读取一行输入
scanner.close();</code>

2. Use the BufferedReader class

• to create a BufferedReader object and pass Enter a Reader object (eg FileReader).
• Use the readLine() method to read the input line by line.
• Similarly, remember to close the BufferedReader object.

Example:

<code class="java">BufferedReader reader = new BufferedReader(new FileReader("input.txt"));
String line;
while ((line = reader.readLine()) != null) {
    // 处理每一行输入
}
reader.close();</code>

3. Use the DataInputStream class

• to create a DataInputStream object and pass Enter an InputStream object (eg FileInputStream).
• Use methods such as readInt() and readUTF() to read specific types of data.
• Make sure to close the DataInputStream object after processing is complete.

Example:

<code class="java">DataInputStream input = new DataInputStream(new FileInputStream("input.dat"));
int number = input.readInt(); // 读取一个整数
String text = input.readUTF(); // 读取一个字符串
input.close();</code>

Other notes:

• Exception handling:When using these methods, be sure to handle exceptions that may occur (such as EOFException, FileNotFoundException).
• Data type conversion: Use methods such as Integer.parseInt() and Double.parseDouble() as needed to convert strings to numeric types.
• Close resources: Use the try-with-resources statement or explicitly call the close() method to close all input objects to release resources.

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