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 Springs,
the behavior of a collection of Springs
can be reduced to that of an ordinary (non-compound) Spring. We define
the "+", "-", max, and min operators on
Springs 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 Springs as [a, b, c],
where a <= b <= c, we can define the same
arithmetic operators on Springs:
[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 Springs 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:
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Field Summary
FieldsModifier and TypeFieldDescriptionstatic final intAn integer value signifying that a property value has not yet been calculated. -
Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionstatic Springconstant(int pref) Returns a strut -- a spring whose minimum, preferred, and maximum values each have the valuepref.static Springconstant(int min, int pref, int max) Returns a spring whose minimum, preferred, and maximum values have the values:min,pref, andmaxrespectively.abstract intReturns the maximum value of thisSpring.abstract intReturns the minimum value of thisSpring.abstract intReturns the preferred value of thisSpring.abstract intgetValue()Returns the current value of thisSpring.static SpringReturns 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 SpringReturnsmax(s1, s2): a spring whose value is always greater than (or equal to) the values of boths1ands2.static SpringReturns-s: a spring running in the opposite direction tos.static SpringReturns a spring whose minimum, preferred, maximum and value properties are each multiples of the properties of the argument spring,s.abstract voidsetValue(int value) Sets the current value of thisSpringtovalue.static SpringReturnss1+s2: a spring representings1ands2in series.static SpringReturns 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.
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Field Details
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UNSET
public static final int UNSETAn integer value signifying that a property value has not yet been calculated.- See Also:
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Constructor Details
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Spring
protected Spring()Used by factory methods to create aSpring.
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Method Details
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getMinimumValue
public abstract int getMinimumValue()Returns the minimum value of thisSpring.- Returns:
- the
minimumValueproperty of thisSpring
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getPreferredValue
public abstract int getPreferredValue()Returns the preferred value of thisSpring.- Returns:
- the
preferredValueof thisSpring
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getMaximumValue
public abstract int getMaximumValue()Returns the maximum value of thisSpring.- Returns:
- the
maximumValueproperty of thisSpring
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getValue
public abstract int getValue()Returns the current value of thisSpring.- Returns:
- the
valueproperty of thisSpring - See Also:
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setValue
public abstract void setValue(int value) Sets the current value of thisSpringtovalue.- Parameters:
value- the new setting of thevalueproperty- See Also:
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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:
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constant
Returns a spring whose minimum, preferred, and maximum values have the values:min,pref, andmaxrespectively.- 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, andmaxrespectively - See Also:
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minus
Returns-s: a spring running in the opposite direction tos.- Parameters:
s- aSpringobject- Returns:
-s: a spring running in the opposite direction tos- See Also:
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sum
Returnss1+s2: a spring representings1ands2in series. In a sum,s3, of two springs,s1ands2, the strains ofs1,s2, ands3are 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 - minand the strain of a spring in tension is:value - pref ------------ max - prefWhensetValueis called on the sum spring,s3, the strain ins3is calculated using one of the formulas above. Once the strain of the sum is known, the values ofs1ands2are 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 ofs1ands2is exactly equal to the value ofs3.- Parameters:
s1- aSpringobjects2- aSpringobject- Returns:
s1+s2: a spring representings1ands2in series- See Also:
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max
Returnsmax(s1, s2): a spring whose value is always greater than (or equal to) the values of boths1ands2.- Parameters:
s1- aSpringobjects2- aSpringobject- Returns:
max(s1, s2): a spring whose value is always greater than (or equal to) the values of boths1ands2- See Also:
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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 whenfactoris negative (in accordance with the rules of interval arithmetic).When factor is, for example, 0.5f the result represents 'the mid-point' 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
smultiplied byfactor - Throws:
NullPointerException- ifsis null- Since:
- 1.5
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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- ifcis null- Since:
- 1.5
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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- ifcis null- Since:
- 1.5
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