JavaTM 2 Platform Std. Ed. v1.5.0
javax.swing
Class Spring
java.lang.Object
javax.swing.Spring
public abstract class Spring  extends Object
An instance of the 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^{TM}
has been added to the java.beans package.
Please see XMLEncoder .
 Since:
 1.4
 See Also:
SpringLayout ,
SpringLayout.Constraints
Field Summary 
static int 
UNSET
An integer value signifying that a property value has not yet been calculated. 
Constructor Summary 
protected 
Spring()
Used by factory methods to create a Spring . 
Method Summary 
static Spring 
constant(int pref)
Returns a strut  a spring whose minimum, preferred, and
maximum values each have the value pref . 
static Spring 
constant(int min,
int pref,
int max)
Returns a spring whose minimum, preferred, and
maximum values have the values: min , pref ,
and max respectively. 
abstract int 
getMaximumValue()
Returns the maximum value of this Spring . 
abstract int 
getMinimumValue()
Returns the minimum value of this Spring . 
abstract int 
getPreferredValue()
Returns the preferred value of this Spring . 
abstract int 
getValue()
Returns the current value of this Spring . 
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)
Returns max(s1, s2) : a spring whose value is always greater than (or equal to)
the values of both s1 and s2 . 
static Spring 
minus(Spring s)
Returns s : a spring running in the opposite direction to s . 
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 this Spring to value . 
static Spring 
sum(Spring s1,
Spring s2)
Returns s1+s2 : a spring representing s1 and s2
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. 
Methods inherited from class java.lang.Object 
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait 
UNSET
public static final int UNSET
 An integer value signifying that a property value has not yet been calculated.
 See Also:
 Constant Field Values
Spring
protected Spring()
 Used by factory methods to create a
Spring .
 See Also:
constant(int) ,
constant(int, int, int) ,
max(javax.swing.Spring, javax.swing.Spring) ,
minus(javax.swing.Spring) ,
sum(javax.swing.Spring, javax.swing.Spring) ,
SpringLayout.Constraints
getMinimumValue
public abstract int getMinimumValue()
 Returns the minimum value of this
Spring .
 Returns:
 the
minimumValue property of this Spring
getPreferredValue
public abstract int getPreferredValue()
 Returns the preferred value of this
Spring .
 Returns:
 the
preferredValue of this Spring
getMaximumValue
public abstract int getMaximumValue()
 Returns the maximum value of this
Spring .
 Returns:
 the
maximumValue property of this Spring
getValue
public abstract int getValue()
 Returns the current value of this
Spring .
 Returns:
 the
value property of this Spring  See Also:
setValue(int)
setValue
public abstract void setValue(int value)
 Sets the current value of this
Spring to value .
 Parameters:
value  the new setting of the value 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 value
pref .
 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 ,
and max 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 ,
and max respectively  See Also:
Spring
minus
public static Spring minus(Spring s)
 Returns
s : a spring running in the opposite direction to s .
 Returns:
s : a spring running in the opposite direction to s  See Also:
Spring
sum
public static Spring sum(Spring s1,
Spring s2)
 Returns
s1+s2 : a spring representing s1 and s2
in series. In a sum, s3 , of two springs, s1 and s2 ,
the strains of s1 , s2 , and s3 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
When setValue is called on the sum spring, s3 , the strain
in s3 is calculated using one of the formulas above. Once the strain of
the sum is known, the values of s1 and s2 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 of s1 and s2 is exactly equal to
the value of s3 .
 Returns:
s1+s2 : a spring representing s1 and s2 in series See Also:
Spring
max
public static Spring max(Spring s1,
Spring s2)
 Returns
max(s1, s2) : a spring whose value is always greater than (or equal to)
the values of both s1 and s2 .
 Returns:
max(s1, s2) : a spring whose value is always greater than (or equal to)
the values of both s1 and s2  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 when factor 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 by factor
 Throws:
NullPointerException  if s 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  if c 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  if c is null Since:
 1.5
Copyright 2003 Sun Microsystems, Inc. All rights reserved
