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 (non-compound) 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
Modifier and Type | Field | Description |
---|---|---|
static int | UNSET | An integer value signifying that a property value has not yet been calculated. |
Constructor Summary
Modifier | Constructor | Description |
---|---|---|
protected | Spring() | Used by factory methods to create a |
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 value |
static Spring | constant(int min,
int pref,
int max) | Returns a spring whose minimum, preferred, and maximum values have the values: |
abstract int | getMaximumValue() | Returns the maximum value of this |
abstract int | getMinimumValue() | Returns the minimum value of this |
abstract int | getPreferredValue() | Returns the preferred value of this |
abstract int | getValue() | Returns the current value of this |
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 |
static Spring | minus(Spring s) | Returns |
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, |
abstract void | setValue(int value) | Sets the current value of this |
static Spring | sum(Spring s1,
Spring s2) | Returns |
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 declared in class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
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
Constructor Detail
Spring
protected Spring()
Used by factory methods to create a Spring
.
Method Detail
getMinimumValue
public abstract int getMinimumValue()
Returns the minimum value of this Spring
.
- Returns:
- the
minimumValue
property of thisSpring
getPreferredValue
public abstract int getPreferredValue()
Returns the preferred value of this Spring
.
- Returns:
- the
preferredValue
of thisSpring
getMaximumValue
public abstract int getMaximumValue()
Returns the maximum value of this Spring
.
- Returns:
- the
maximumValue
property of thisSpring
getValue
public abstract int getValue()
Returns the current value of this Spring
.
- Returns:
- the
value
property of thisSpring
- 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 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 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 spring -
pref
- the preferred value of the new spring -
max
- 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)
Returns -s
: a spring running in the opposite direction to s
.
- 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)
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 - minand the strain of a spring in tension is:
value - pref ------------ max - prefWhen
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
. - Parameters:
-
s1
- aSpring
object -
s2
- aSpring
object - Returns:
-
s1+s2
: a spring representings1
ands2
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
.
- Parameters:
-
s1
- aSpring
object -
s2
- 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 when factor
is 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 scale -
factor
- 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