public abstract class Spring extends Object
Spring
class holds three properties that
characterize its behavior: the minimum, preferred, and
maximum values. Each of these properties may be involved in
defining its fourth, value, property based on a series of rules.
An instance of the Spring
class can be visualized as a
mechanical spring that provides a corrective force as the spring is compressed
or stretched away from its preferred value. This force is modelled
as linear function of the distance from the preferred value, but with
two different constants  one for the compressional force and one for the
tensional one. Those constants are specified by the minimum and maximum
values of the spring such that a spring at its minimum value produces an
equal and opposite force to that which is created when it is at its
maximum value. The difference between the preferred and
minimum values, therefore, represents the ease with which the
spring can be compressed and the difference between its maximum
and preferred values, indicates the ease with which the
Spring
can be extended.
See the sum(javax.swing.Spring, javax.swing.Spring)
method for details.
By defining simple arithmetic operations on Spring
s,
the behavior of a collection of Spring
s
can be reduced to that of an ordinary (noncompound) Spring
. We define
the "+", "", max, and min operators on
Spring
s so that, in each case, the result is a Spring
whose characteristics bear a useful mathematical relationship to its constituent
springs.
A Spring
can be treated as a pair of intervals
with a single common point: the preferred value.
The following rules define some of the
arithmetic operators that can be applied to intervals
([a, b]
refers to the interval
from a
to b
,
where a <= b
).
[a1, b1] + [a2, b2] = [a1 + a2, b1 + b2] [a, b] = [b, a] max([a1, b1], [a2, b2]) = [max(a1, a2), max(b1, b2)]
If we denote Spring
s as [a, b, c]
,
where a <= b <= c
, we can define the same
arithmetic operators on Spring
s:
[a1, b1, c1] + [a2, b2, c2] = [a1 + a2, b1 + b2, c1 + c2] [a, b, c] = [c, b, a] max([a1, b1, c1], [a2, b2, c2]) = [max(a1, a2), max(b1, b2), max(c1, c2)]
With both intervals and Spring
s we can define "" and min
in terms of negation:
X  Y = X + (Y) min(X, Y) = max(X, Y)
For the static methods in this class that embody the arithmetic
operators, we do not actually perform the operation in question as
that would snapshot the values of the properties of the method's arguments
at the time the static method is called. Instead, the static methods
create a new Spring
instance containing references to
the method's arguments so that the characteristics of the new spring track the
potentially changing characteristics of the springs from which it
was made. This is a little like the idea of a lazy value
in a functional language.
If you are implementing a SpringLayout
you
can find further information and examples in
How to Use SpringLayout,
a section in The Java Tutorial.
Warning:
Serialized objects of this class will not be compatible with
future Swing releases. The current serialization support is
appropriate for short term storage or RMI between applications running
the same version of Swing. As of 1.4, support for long term storage
of all JavaBeans
has been added to the java.beans
package.
Please see XMLEncoder
.
 Since:
 1.4
 See Also:
SpringLayout
,SpringLayout.Constraints

Field Summary
Fields Modifier and Type Field Description static int
UNSET
An integer value signifying that a property value has not yet been calculated. 
Constructor Summary
Constructors Modifier Constructor Description protected
Spring()
Used by factory methods to create aSpring
. 
Method Summary
Modifier and Type Method Description static Spring
constant(int pref)
Returns a strut  a spring whose minimum, preferred, and maximum values each have the valuepref
.static Spring
constant(int min, int pref, int max)
Returns a spring whose minimum, preferred, and maximum values have the values:min
,pref
, andmax
respectively.abstract int
getMaximumValue()
Returns the maximum value of thisSpring
.abstract int
getMinimumValue()
Returns the minimum value of thisSpring
.abstract int
getPreferredValue()
Returns the preferred value of thisSpring
.abstract int
getValue()
Returns the current value of thisSpring
.static Spring
height(Component c)
Returns a spring whose minimum, preferred, maximum and value properties are defined by the heights of the minimumSize, preferredSize, maximumSize and size properties of the supplied component.static Spring
max(Spring s1, Spring s2)
Returnsmax(s1, s2)
: a spring whose value is always greater than (or equal to) the values of boths1
ands2
.static Spring
minus(Spring s)
Returnss
: a spring running in the opposite direction tos
.static Spring
scale(Spring s, float factor)
Returns a spring whose minimum, preferred, maximum and value properties are each multiples of the properties of the argument spring,s
.abstract void
setValue(int value)
Sets the current value of thisSpring
tovalue
.static Spring
sum(Spring s1, Spring s2)
Returnss1+s2
: a spring representings1
ands2
in series.static Spring
width(Component c)
Returns a spring whose minimum, preferred, maximum and value properties are defined by the widths of the minimumSize, preferredSize, maximumSize and size properties of the supplied component.

Field Details

UNSET
public static final int UNSETAn integer value signifying that a property value has not yet been calculated. See Also:
 Constant Field Values


Constructor Details

Spring
protected Spring()Used by factory methods to create aSpring
.


Method Details

getMinimumValue
public abstract int getMinimumValue()Returns the minimum value of thisSpring
. Returns:
 the
minimumValue
property of thisSpring

getPreferredValue
public abstract int getPreferredValue()Returns the preferred value of thisSpring
. Returns:
 the
preferredValue
of thisSpring

getMaximumValue
public abstract int getMaximumValue()Returns the maximum value of thisSpring
. Returns:
 the
maximumValue
property of thisSpring

getValue
public abstract int getValue()Returns the current value of thisSpring
. Returns:
 the
value
property of thisSpring
 See Also:
setValue(int)

setValue
public abstract void setValue(int value)Sets the current value of thisSpring
tovalue
. Parameters:
value
 the new setting of thevalue
property See Also:
getValue()

constant
Returns a strut  a spring whose minimum, preferred, and maximum values each have the valuepref
. Parameters:
pref
 the minimum, preferred, and maximum values of the new spring Returns:
 a spring whose minimum, preferred, and
maximum values each have the value
pref
 See Also:
Spring

constant
Returns a spring whose minimum, preferred, and maximum values have the values:min
,pref
, andmax
respectively. Parameters:
min
 the minimum value of the new springpref
 the preferred value of the new springmax
 the maximum value of the new spring Returns:
 a spring whose minimum, preferred, and
maximum values have the values:
min
,pref
, andmax
respectively  See Also:
Spring

minus
Returnss
: a spring running in the opposite direction tos
. Parameters:
s
 aSpring
object Returns:
s
: a spring running in the opposite direction tos
 See Also:
Spring

sum
Returnss1+s2
: a spring representings1
ands2
in series. In a sum,s3
, of two springs,s1
ands2
, the strains ofs1
,s2
, ands3
are maintained at the same level (to within the precision implied by their integer values). The strain of a spring in compression is:value  pref  pref  min
and the strain of a spring in tension is:value  pref  max  pref
WhensetValue
is called on the sum spring,s3
, the strain ins3
is calculated using one of the formulas above. Once the strain of the sum is known, the values ofs1
ands2
are then set so that they are have a strain equal to that of the sum. The formulas are evaluated so as to take rounding errors into account and ensure that the sum of the values ofs1
ands2
is exactly equal to the value ofs3
. Parameters:
s1
 aSpring
objects2
 aSpring
object Returns:
s1+s2
: a spring representings1
ands2
in series See Also:
Spring

max
Returnsmax(s1, s2)
: a spring whose value is always greater than (or equal to) the values of boths1
ands2
. Parameters:
s1
 aSpring
objects2
 aSpring
object Returns:
max(s1, s2)
: a spring whose value is always greater than (or equal to) the values of boths1
ands2
 See Also:
Spring

scale
Returns a spring whose minimum, preferred, maximum and value properties are each multiples of the properties of the argument spring,s
. Minimum and maximum properties are swapped whenfactor
is negative (in accordance with the rules of interval arithmetic).When factor is, for example, 0.5f the result represents 'the midpoint' of its input  an operation that is useful for centering components in a container.
 Parameters:
s
 the spring to scalefactor
 amount to scale by. Returns:
 a spring whose properties are those of the input spring
s
multiplied byfactor
 Throws:
NullPointerException
 ifs
is null Since:
 1.5

width
Returns a spring whose minimum, preferred, maximum and value properties are defined by the widths of the minimumSize, preferredSize, maximumSize and size properties of the supplied component. The returned spring is a 'wrapper' implementation whose methods call the appropriate size methods of the supplied component. The minimum, preferred, maximum and value properties of the returned spring therefore report the current state of the appropriate properties in the component and track them as they change. Parameters:
c
 Component used for calculating size Returns:
 a spring whose properties are defined by the horizontal component of the component's size methods.
 Throws:
NullPointerException
 ifc
is null Since:
 1.5

height
Returns a spring whose minimum, preferred, maximum and value properties are defined by the heights of the minimumSize, preferredSize, maximumSize and size properties of the supplied component. The returned spring is a 'wrapper' implementation whose methods call the appropriate size methods of the supplied component. The minimum, preferred, maximum and value properties of the returned spring therefore report the current state of the appropriate properties in the component and track them as they change. Parameters:
c
 Component used for calculating size Returns:
 a spring whose properties are defined by the vertical component of the component's size methods.
 Throws:
NullPointerException
 ifc
is null Since:
 1.5
