 java.lang.Object

 javax.swing.Spring

public abstract class Spring extends Object
An instance of theSpring
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 theSpring
can be extended. See thesum(javax.swing.Spring, javax.swing.Spring)
method for details.By defining simple arithmetic operations on
Spring
s, the behavior of a collection ofSpring
s can be reduced to that of an ordinary (noncompound)Spring
. We define the "+", "", max, and min operators onSpring
s so that, in each case, the result is aSpring
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 froma
tob
, wherea <= 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]
, wherea <= b <= c
, we can define the same arithmetic operators onSpring
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 seeXMLEncoder
. 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 Detail

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


Method Detail

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
public static Spring constant(int pref)
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
public 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. 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
public static Spring minus(Spring s)
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
public static Spring sum(Spring s1, Spring s2)
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
public 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
. 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
public 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
. 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
public 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. 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
public 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. 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

