Java : FilterReader con ejemplos

FilterReader (Java SE 22 & JDK 22) en Java con ejemplos.
Encontrará ejemplos de código en la mayoría de los métodos de FilterReader.

Nota :

Este artículo puede utilizar software de traducción para su comodidad. Consulte también la versión original en inglés.

Summary

Clase abstracta para leer secuencias de caracteres filtrados. La clase abstracta FilterReader proporciona métodos predeterminados que pasan todas las solicitudes a la secuencia contenida. Las subclases de FilterReader deberían anular algunos de estos métodos y también pueden proporcionar métodos y campos adicionales. (Traducción automática)

Class diagram

class MyReader extends FilterReader {
    MyReader(Reader in) {
        super(in);
    }
}

try (final var reader = new MyReader(new StringReader("abc"))) {
    System.out.printf("%c%n", reader.read()); // a
    System.out.printf("%c%n", reader.read()); // b
    System.out.printf("%c%n", reader.read()); // c
    System.out.println(reader.read()); // -1
}

Fields

protected Reader in

El flujo de entrada de caracteres subyacente. (Traducción automática)

class MyReader extends FilterReader {
    MyReader(Reader in) {
        super(in);
    }

    Reader getIn() {
        return in;
    }
}

final var sr = new StringReader("abc");
try (final var reader = new MyReader(sr)) {
    System.out.println(reader.getIn() == sr); // true
}

Fields declared in Reader

lock

Consulte el siguiente enlace.

Reader con ejemplos

Constructors

FilterReader (Reader in)

Crea un nuevo lector filtrado. (Traducción automática)

class MyReader extends FilterReader {
    MyReader(Reader in) {
        super(in);
    }
}

try (final var reader = new MyReader(new StringReader("abc"))) {
    System.out.printf("%c%n", reader.read()); // a
    System.out.printf("%c%n", reader.read()); // b
    System.out.printf("%c%n", reader.read()); // c
    System.out.println(reader.read()); // -1
}

Methods

void close ()

Cierra la transmisión y libera todos los recursos del sistema asociados con ella. (Traducción automática)

class MyReader extends FilterReader {
    MyReader(Reader in) {
        super(in);
    }
}

try (final var reader = new MyReader(new StringReader("abc"))) {
    System.out.printf("%c%n", reader.read()); // a
    System.out.printf("%c%n", reader.read()); // b
    System.out.printf("%c%n", reader.read()); // c
    System.out.println(reader.read()); // -1
}

// An example without a try-with-resources statement.
class MyReader extends FilterReader {
    MyReader(Reader in) {
        super(in);
    }
}

final var reader = new MyReader(new StringReader("abc"));
try {
    System.out.printf("%c%n", reader.read()); // a
    System.out.printf("%c%n", reader.read()); // b
    System.out.printf("%c%n", reader.read()); // c
    System.out.println(reader.read()); // -1
} finally {
    reader.close();
}

void mark (int readAheadLimit)

Marca la posición actual en la secuencia. (Traducción automática)

class MyReader extends FilterReader {
    MyReader(Reader in) {
        super(in);
    }
}

try (final var reader = new MyReader(new BufferedReader(new StringReader("abcde")))) {
    System.out.printf("%c%n", reader.read()); // a
    System.out.printf("%c%n", reader.read()); // b
    System.out.printf("%c%n", reader.read()); // c

    reader.mark(3);

    System.out.printf("%c%n", reader.read()); // d
    System.out.printf("%c%n", reader.read()); // e
    System.out.println(reader.read()); // -1

    reader.reset();

    System.out.printf("%c%n", reader.read()); // d
    System.out.printf("%c%n", reader.read()); // e
    System.out.println(reader.read()); // -1

    reader.reset();
    reader.mark(2);

    System.out.printf("%c%n", reader.read()); // d
    System.out.printf("%c%n", reader.read()); // e
    System.out.println(reader.read()); // -1

    try {
        reader.reset();
    } catch (IOException e) {
        System.out.println("IOException! : " + e.getMessage());
    }

    // Result
    // ↓
    //IOException! : Mark invalid
}

boolean markSupported ()

Indica si esta secuencia admite la operación mark(). (Traducción automática)

class MyReader extends FilterReader {
    MyReader(Reader in) {
        super(in);
    }
}

{
    final var path = Path.of("R:", "java-work", "aaa.txt");
    System.out.println(path); // R:\java-work\aaa.txt

    Files.writeString(path, "abcd");

    try (final var reader = new MyReader(Files.newBufferedReader(path))) {
        System.out.println(reader.markSupported()); // true
    }
}
{
    try (final var reader = new MyReader(new StringReader("abcd"))) {
        System.out.println(reader.markSupported()); // true
    }
}
{
    final var url = URI.create("https://example.com/").toURL();
    try (final var reader = new MyReader(new InputStreamReader(url.openStream()))) {
        System.out.println(reader.markSupported()); // false
    }
}

int read ()

Lee un solo caracter. (Traducción automática)

class MyReader extends FilterReader {
    MyReader(Reader in) {
        super(in);
    }
}

try (final var reader = new MyReader(new StringReader("abc"))) {
    System.out.printf("%c%n", reader.read()); // a
    System.out.printf("%c%n", reader.read()); // b
    System.out.printf("%c%n", reader.read()); // c
    System.out.println(reader.read()); // -1
}

int read (char[] cbuf, int off, int len)

Lee caracteres en una parte de una matriz. (Traducción automática)

class MyReader extends FilterReader {
    MyReader(Reader in) {
        super(in);
    }
}

try (final var reader = new MyReader(new StringReader("abcdefg"))) {
    final var cbuf = new char[5];

    System.out.println(reader.read(cbuf, 0, 1)); // 1
    System.out.println(Arrays.toString(cbuf)); // [a,  ,  ,  ,  ]

    System.out.println(reader.read(cbuf, 0, 2)); // 2
    System.out.println(Arrays.toString(cbuf)); // [b, c,  ,  ,  ]

    System.out.println(reader.read(cbuf, 0, 3)); // 3
    System.out.println(Arrays.toString(cbuf)); // [d, e, f,  ,  ]

    System.out.println(reader.read(cbuf, 0, 4)); // 1
    System.out.println(Arrays.toString(cbuf)); // [g, e, f,  ,  ]

    System.out.println(reader.read(cbuf, 0, 5)); // -1
    System.out.println(Arrays.toString(cbuf)); // [g, e, f,  ,  ]
}

try (final var reader = new MyReader(new StringReader("abcde"))) {
    final var cbuf = new char[5];

    System.out.println(reader.read(cbuf, 4, 1)); // 1
    System.out.println(Arrays.toString(cbuf)); // [ ,  ,  ,  , a]

    System.out.println(reader.read(cbuf, 3, 1)); // 1
    System.out.println(Arrays.toString(cbuf)); // [ ,  ,  , b, a]

    System.out.println(reader.read(cbuf, 2, 1)); // 1
    System.out.println(Arrays.toString(cbuf)); // [ ,  , c, b, a]

    System.out.println(reader.read(cbuf, 1, 1)); // 1
    System.out.println(Arrays.toString(cbuf)); // [ , d, c, b, a]

    System.out.println(reader.read(cbuf, 0, 1)); // 1
    System.out.println(Arrays.toString(cbuf)); // [e, d, c, b, a]
}

try (final var reader = new MyReader(new StringReader("abcdefg"))) {
    final var cbuf = new char[3];

    System.out.println(reader.read(cbuf, 0, 3)); // 3
    System.out.println(Arrays.toString(cbuf)); // [a, b, c]

    //reader.read(cbuf, 0, 4); // IndexOutOfBoundsException
    //reader.read(cbuf, 3, 1); // IndexOutOfBoundsException
}

boolean ready ()

Indica si esta secuencia está lista para ser leída. (Traducción automática)

class MyReader extends FilterReader {
    MyReader(Reader in) {
        super(in);
    }
}

final var path = Path.of("R:", "java-work", "aaa.txt");
System.out.println(path); // R:\java-work\aaa.txt

Files.writeString(path, "abc");

try (final var reader = new MyReader(Files.newBufferedReader(path))) {
    System.out.println(reader.ready()); // true
    System.out.printf("%c%n", reader.read()); // a

    System.out.println(reader.ready()); // true
    System.out.printf("%c%n", reader.read()); // b

    System.out.println(reader.ready()); // true
    System.out.printf("%c%n", reader.read()); // c

    System.out.println(reader.ready()); // false
    System.out.println(reader.read()); // -1
}

void reset ()

Restablece la transmisión. (Traducción automática)

class MyReader extends FilterReader {
    MyReader(Reader in) {
        super(in);
    }
}

try (final var reader = new MyReader(new BufferedReader(new StringReader("abcde")))) {
    System.out.printf("%c%n", reader.read()); // a
    System.out.printf("%c%n", reader.read()); // b
    System.out.printf("%c%n", reader.read()); // c

    reader.mark(3);

    System.out.printf("%c%n", reader.read()); // d
    System.out.printf("%c%n", reader.read()); // e
    System.out.println(reader.read()); // -1

    reader.reset();

    System.out.printf("%c%n", reader.read()); // d
    System.out.printf("%c%n", reader.read()); // e
    System.out.println(reader.read()); // -1

    reader.reset();
    reader.mark(2);

    System.out.printf("%c%n", reader.read()); // d
    System.out.printf("%c%n", reader.read()); // e
    System.out.println(reader.read()); // -1

    try {
        reader.reset();
    } catch (IOException e) {
        System.out.println("IOException! : " + e.getMessage());
    }

    // Result
    // ↓
    //IOException! : Mark invalid
}

long skip (long n)

Salta caracteres. (Traducción automática)

class MyReader extends FilterReader {
    MyReader(Reader in) {
        super(in);
    }
}

try (final var reader = new MyReader(new StringReader("abcdefghij"))) {
    System.out.printf("%c%n", reader.read()); // a

    System.out.println(reader.skip(1)); // 1
    System.out.printf("%c%n", reader.read()); // c

    System.out.println(reader.skip(2)); // 2
    System.out.printf("%c%n", reader.read()); // f

    System.out.println(reader.skip(3)); // 3
    System.out.printf("%c%n", reader.read()); // j

    System.out.println(reader.skip(1)); // 0
    System.out.println(reader.read()); // -1
}

try (final var reader = new MyReader(new StringReader("abcde"))) {
    System.out.printf("%c%n", reader.read()); // a

    System.out.println(reader.skip(10)); // 4
    System.out.println(reader.read()); // -1
}

Methods declared in Reader

nullReader, read, read, transferTo

Consulte el siguiente enlace.

Reader con ejemplos

Ejemplos de API

Java : FilterReader con ejemplos

Summary

Fields

protected Reader in

Fields declared in Reader

lock

Constructors

FilterReader (Reader in)

Methods

void close ()

void mark (int readAheadLimit)

boolean markSupported ()

int read ()

int read (char[] cbuf, int off, int len)

boolean ready ()

void reset ()

long skip (long n)

Methods declared in Reader

nullReader, read, read, transferTo

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