Java {R.utils} | R Documentation

## Static class for Java related methods

### Description

Package: R.utils
Class Java

`Object`
`~~|`
`~~+--``Java`

Directly known subclasses:

public static class Java
extends Object

Static class that provides methods for reading and writing Java data types. Currently the following data types are supported: byte, short and int. R character strings can be written as UTF-8 formatted strings, which can be read by Java. Currently on Java String's that contain ASCII characters can be imported into R. The reason for this is that other characters are translated into non-eight bits data, e.g. 16- and 24-bits, which the readChar() method currently does not support.

Furthermore, the Java class defines some static constants describing the minimum and maximum value of some of the common Java data types: `BYTE.MIN`, `BYTE.MAX` `SHORT.MIN`, `SHORT.MAX` `INT.MIN`, `INT.MAX` `LONG.MIN`, and `LONG.MAX`.

### Usage

    Java()

### Fields and Methods

Methods:

| `asByte` | Converts a numeric to a Java byte.
| `asInt` | Converts an numeric to a Java integer.
| `asLong` | Converts a numeric to a Java long.
| `asShort` | Converts a numeric to a Java short.
| `readByte` | Reads a Java formatted byte (8 bits) from a connection.
| `readInt` | Reads a Java formatted int (32 bits) from a connection.
| `readShort` | Reads a Java formatted short (16 bits) from a connection.
| `readUTF` | Reads a Java (UTF-8) formatted string from a connection.
| `writeByte` | Writes a byte (8 bits) to a connection in Java format.
| `writeInt` | Writes a integer (32 bits) to a connection in Java format.
| `writeShort` | Writes a short (16 bits) to a connection in Java format.
| `writeUTF` | Writes a string to a connection in Java format (UTF-8).

Methods inherited from Object:
$, $<-, [[, [[<-, as.character, attach, attachLocally, clearCache, clearLookupCache, clone, detach, equals, extend, finalize, getEnvironment, getFieldModifier, getFieldModifiers, getFields, getInstantiationTime, getStaticInstance, hasField, hashCode, ll, load, names, objectSize, print, save

### Author(s)

Henrik Bengtsson

### Examples

    pathname <- tempfile()

    # Open the temporary file for writing
    out <- file(pathname, open="wb")
    b <- -128:127
    Java$writeByte(out, b)
    s <- -32768:32767
    Java$writeShort(out, s)
    i <- c(-2147483648, -2147483647, -1, 0, +1, 2147483646, 2147483647);
    Java$writeInt(out, i)
    str <- c("This R string was written (using the UTF-8 format) using",
             "the static methods of the Java class in the R.io package.")
    str <- paste(str, collapse="\n")
    Java$writeUTF(out, str)
    close(out)

    # Open the temporary file for reading
    inn <- file(pathname, open="rb")

    bfr <- Java$readByte(inn, n=length(b))
    cat("Read ", length(bfr), " bytes.\n", sep="")
    if (!identical(bfr, b))
      throw("Failed to read the same data that was written.")

    bfr <- Java$readShort(inn, n=length(s))
    cat("Read ", length(bfr), " shorts.\n", sep="")
    if (!identical(bfr, s))
      throw("Failed to read the same data that was written.")

    bfr <- Java$readInt(inn, n=length(i))
    cat("Read ", length(bfr), " ints.\n", sep="")
    if (!identical(bfr, i))
      throw("Failed to read the same data that was written.")

    bfr <- Java$readUTF(inn)
    cat("Read ", nchar(bfr), " UTF characters:\n", "'", bfr, "'\n", sep="")

    close(inn)

    file.remove(pathname)

[Package R.utils version 2.6.0 Index]