ucar.units.Dimension Maven / Gradle / Ivy
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/*
* Copyright (c) 1998-2018 University Corporation for Atmospheric Research/Unidata
* See LICENSE for license information.
*/
package ucar.units;
/**
* Provides support for the concept of "dimension": pairs of base entities and
* exponents.
*
* @author Steven R. Emmerson
*/
public abstract class Dimension {
/**
* The individual elements of this dimension.
*
* @serial
*/
protected final Factor[] _factors;
private transient volatile int hashCode;
/**
* Constructs a dimensionless dimension from nothing.
*/
public Dimension() {
this(new Factor[0]);
}
/**
* Constructs from a single Factor.
*
* @param factor
* The single Factor that defines the dimension.
*/
protected Dimension(final Factor factor) {
this(new Factor[] {factor});
}
/**
* Constructs from an array of Factor-s. This is a trusted constructor for
* use by subclasses only.
*
* @param factors
* The factors that define the dimension.
*/
protected Dimension(final Factor[] factors) {
_factors = factors;
}
/**
* Returns the rank of this dimension. The rank is the number of base entity
* and exponent pairs (i.e. the number of Factor-s constituting this
* dimension).
*
* @return The rank of this dimension.
*/
public final int getRank() {
return _factors.length;
}
/**
* Returns the array of Factor-s constituting this dimension.
*
* @return The array of Factor-s constituting this dimension.
*/
public final Factor[] getFactors() {
final Factor[] factors = new Factor[_factors.length];
System.arraycopy(_factors, 0, factors, 0, factors.length);
return factors;
}
/**
* Multiplies this dimension by another dimension.
*
* @param that
* The other dimension.
* @return The product of the Factor-s of this dimension and the Factor-s of
* the other dimension.
*/
protected Factor[] mult(final Dimension that) {
// relys on _factors always sorted
final Factor[] factors1 = _factors;
final Factor[] factors2 = that._factors;
int i1 = 0;
int i2 = 0;
int k = 0;
Factor[] newFactors = new Factor[factors1.length + factors2.length];
for (;;) {
if (i1 == factors1.length) {
final int n = factors2.length - i2;
System.arraycopy(factors2, i2, newFactors, k, n);
k += n;
break;
}
if (i2 == factors2.length) {
final int n = factors1.length - i1;
System.arraycopy(factors1, i1, newFactors, k, n);
k += n;
break;
}
final Factor f1 = factors1[i1];
final Factor f2 = factors2[i2];
final int comp = f1.getID().compareTo(f2.getID());
if (comp < 0) {
newFactors[k++] = f1;
i1++;
} else if (comp == 0) {
final int exponent = f1.getExponent() + f2.getExponent();
if (exponent != 0) {
newFactors[k++] = new Factor(f1, exponent);
}
i1++;
i2++;
} else {
newFactors[k++] = f2;
i2++;
}
}
if (k < newFactors.length) {
final Factor[] tmp = new Factor[k];
System.arraycopy(newFactors, 0, tmp, 0, k);
newFactors = tmp;
}
return newFactors;
}
/**
* Raises this dimension to a power.
*
* @param power
* The power to raise this dimension by.
* @return The Factor-s of this dimension raised to the power
* power.
*/
protected Factor[] pow(final int power) {
Factor[] factors;
if (power == 0) {
factors = new Factor[0];
} else {
factors = getFactors();
if (power != 1) {
for (int i = factors.length; --i >= 0;) {
factors[i] = factors[i].pow(power);
}
}
}
return factors;
}
/**
* Indicates if this Dimension is the reciprocal of another dimension.
*
* @param that
* The other dimension.
* @return true if and only if this dimension is the reciprocal
* of the other dimension.
*/
public final boolean isReciprocalOf(final Dimension that) {
final Factor[] theseFactors = _factors;
final Factor[] thoseFactors = that._factors;
boolean isReciprocalOf;
if (theseFactors.length != thoseFactors.length) {
isReciprocalOf = false;
} else {
int i;
for (i = theseFactors.length; --i >= 0;) {
if (!theseFactors[i].isReciprocalOf(thoseFactors[i])) {
break;
}
}
isReciprocalOf = i < 0;
}
return isReciprocalOf;
}
/**
* Indicates if this dimension is semantically identical to an object.
*
* @param object
* The object.
* @return true if and only if this dimension is semantically
* identical to object.
*/
@Override
public final boolean equals(final Object object) {
boolean equals;
if (this == object) {
equals = true;
} else if (!(object instanceof Dimension)) {
equals = false;
} else {
final Factor[] thatFactors = ((Dimension) object)._factors;
if (_factors.length != thatFactors.length) {
equals = false;
} else {
int i = _factors.length;
while (--i >= 0) {
if (!_factors[i].equals(thatFactors[i])) {
break;
}
}
equals = i < 0;
}
}
return equals;
}
/**
* Returns the hash code of this instance.
*
* @return The hash code of this instance.
*/
@Override
public int hashCode() {
if (hashCode == 0) {
int hash = 0;
for (Factor factor : _factors) {
hash ^= factor.hashCode();
}
hashCode = hash;
}
return hashCode;
}
/**
* Indicates if this dimension is dimensionless. A dimension is
* dimensionless if it has no Factor-s or if all Factor-s are, themselves,
* dimensionless.
*
* @return true if and only if this dimension is dimensionless.
*/
public final boolean isDimensionless() {
for (int i = _factors.length; --i >= 0;) {
if (!_factors[i].isDimensionless()) {
return false;
}
}
return true;
}
/**
* Returns the string representation of this dimension.
*
* @return The string representation of this dimension.
*/
@Override
public String toString() {
final StringBuilder buf = new StringBuilder(40);
for (Factor factor : _factors) {
buf.append(factor).append('.');
}
if (buf.length() != 0) {
buf.setLength(buf.length() - 1);
}
return buf.toString();
}
}
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