Wrap numeric vector as flat Java parameter
.jfloat marks a numeric vector as an object that can be used
as parameter to Java calls that require float parameters.
Similarly, .jlong marks a numeric vector as long
parameter, .jshort as short and .jbyte as
byte.
.jfloat(x) .jlong(x) .jbyte(x) .jchar(x) .jshort(x)
x |
numeric vector |
R has no native float or long type. Numeric vectors are
stored as doubles, hence there is no native way to pass float
numbers to Java methods. The .jfloat call marks a numeric
vector as having the Java type float by wrapping it in the
jfloat class. The class is still a subclass of numeric,
therefore all regular R operations are unaffected by this.
Similarly, .jlong is used to mark a numeric vector as a
parameter of the long Java type. Please note that in general R
has no native type that will hold a long value, so conversion
between Java's long type and R's numeric is potentially lossy.
.jbyte is used when a scalar byte is to be passed to Java. Note
that byte arrays are natively passed as raw vectors, not as
.jbyte arrays, although non-scalar .jbyte is equivalent
except for using four-times as much memory.
.jchar is strictly experimental and uses integer vector as
storage class. The type char in Java
represents 16-bit Unicode code points (not to be confused with
char in C which is byte in Java!), see Java
documentation for details. x can also be a non-NA string
in which case .jchar(x) is just a shorthand for
.jnew("java.lang.String", x)$toCharArray() and thus performs a
Java call (unlike all other functions mentioned here).
Returns a numeric vector of the class jfloat, jlong,
jbyte, jshort or jchar
that can be used as parameter to Java calls that require
float, long, byte, short or char
parameters respectively.
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