Predefined Streams and Using Byte Streams

Predefined Flows:

• System class: The java.lang package automatically imports the System class, which represents the Java runtime environment.
• Flow Variables: Contains three predefined flows: System.in, System.out and System.err.
• System.out: Standard output stream (typically the console).
• System.in: Default input stream (typically the keyboard).
• System.err: Standard error stream (also the console).

Types of Flows:

• System.in is of type InputStream.
• System.out and System.err are of type PrintStream.
• These are all byte streams, but can be encapsulated in character streams.

Example:

System.out.println("Este é o fluxo de saída padrão.");
System.err.println("Este é o fluxo de erro.");
int dado = System.in.read(); // Lê um byte do teclado

Use of Byte Streams:

Byte Stream Hierarchy:

• InputStream and OutputStream are at the top of the hierarchy.
• They offer basic I/O methods, which can throw IOException in case of an error.
• Character Flows Preference:
• Although byte streams can be used to read from the console, character streams are recommended to facilitate internationalization and maintainability.
• When to use Byte Streams:
• Suitable for example programs, simple utilities and for operations with raw keyboard input.

Example of Console Reading with Byte Stream:

try {
    InputStream input = System.in;
    System.out.print("Digite um caractere: ");
    int caractere = input.read(); // Lê um byte do console
    System.out.println("Você digitou: " + (char) caractere);
} catch (IOException e) {
    System.err.println("Erro ao ler o caractere.");
}

This excerpt emphasizes that predefined streams are fundamental in Java and introduces the basic use of byte streams for simple input and output operations.

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