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	/*
	* Copyright (c) 2001, 2013, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/
	package javax.swing;

	import java.awt.Component;

	/**
	* An instance of the <code>Spring</code> class holds three properties that
	* characterize its behavior: the <em>minimum</em>, <em>preferred</em>, and
	* <em>maximum</em> values. Each of these properties may be involved in
	* defining its fourth, <em>value</em>, property based on a series of rules.
	* <p>
	* An instance of the <code>Spring</code> 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 <em>preferred</em> and
	* <em>minimum</em> values, therefore, represents the ease with which the
	* spring can be compressed and the difference between its <em>maximum</em>
	* and <em>preferred</em> values, indicates the ease with which the
	* <code>Spring</code> can be extended.
	* See the {@link #sum} method for details.
	*
	* <p>
	* By defining simple arithmetic operations on <code>Spring</code>s,
	* the behavior of a collection of <code>Spring</code>s
	* can be reduced to that of an ordinary (non-compound) <code>Spring</code>. We define
	* the "+", "-", <em>max</em>, and <em>min</em> operators on
	* <code>Spring</code>s so that, in each case, the result is a <code>Spring</code>
	* whose characteristics bear a useful mathematical relationship to its constituent
	* springs.
	*
	* <p>
	* A <code>Spring</code> 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
	* (<code>[a, b]</code> refers to the interval
	* from <code>a</code>
	* to <code>b</code>,
	* where <code>a <= b</code>).
	*
	* <pre>
	* [a1, b1] + [a2, b2] = [a1 + a2, b1 + b2]
	*
	* -[a, b] = [-b, -a]
	*
	* max([a1, b1], [a2, b2]) = [max(a1, a2), max(b1, b2)]
	* </pre>
	* <p>
	*
	* If we denote <code>Spring</code>s as <code>[a, b, c]</code>,
	* where <code>a <= b <= c</code>, we can define the same
	* arithmetic operators on <code>Spring</code>s:
	*
	* <pre>
	* [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)]
	* </pre>
	* <p>
	* With both intervals and <code>Spring</code>s we can define "-" and <em>min</em>
	* in terms of negation:
	*
	* <pre>
	* X - Y = X + (-Y)
	*
	* min(X, Y) = -max(-X, -Y)
	* </pre>
	* <p>
	* 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 <code>Spring</code> 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 <em>lazy value</em>
	* in a functional language.
	* <p>
	* If you are implementing a <code>SpringLayout</code> you
	* can find further information and examples in
	* <a
	href="https://docs.oracle.com/javase/tutorial/uiswing/layout/spring.html">How to Use SpringLayout</a>,
	* a section in <em>The Java Tutorial.</em>
	* <p>
	* <strong>Warning:</strong>
	* 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 <code>java.beans</code> package.
	* Please see {@link java.beans.XMLEncoder}.
	*
	* @see SpringLayout
	* @see SpringLayout.Constraints
	*
	* @author Philip Milne
	* @since 1.4
	*/
	public abstract class Spring {

	/**
	* An integer value signifying that a property value has not yet been calculated.
	*/
	public static final int UNSET = Integer.MIN_VALUE;

	/**
	* Used by factory methods to create a <code>Spring</code>.
	*
	* @see #constant(int)
	* @see #constant(int, int, int)
	* @see #max
	* @see #minus
	* @see #sum
	* @see SpringLayout.Constraints
	*/
	protected Spring() {}

	/**
	* Returns the <em>minimum</em> value of this <code>Spring</code>.
	*
	* @return the <code>minimumValue</code> property of this <code>Spring</code>
	*/
	public abstract int getMinimumValue();

	/**
	* Returns the <em>preferred</em> value of this <code>Spring</code>.
	*
	* @return the <code>preferredValue</code> of this <code>Spring</code>
	*/
	public abstract int getPreferredValue();

	/**
	* Returns the <em>maximum</em> value of this <code>Spring</code>.
	*
	* @return the <code>maximumValue</code> property of this <code>Spring</code>
	*/
	public abstract int getMaximumValue();

	/**
	* Returns the current <em>value</em> of this <code>Spring</code>.
	*
	* @return the <code>value</code> property of this <code>Spring</code>
	*
	* @see #setValue
	*/
	public abstract int getValue();

	/**
	* Sets the current <em>value</em> of this <code>Spring</code> to <code>value</code>.
	*
	* @param value the new setting of the <code>value</code> property
	*
	* @see #getValue
	*/
	public abstract void setValue(int value);

	private double range(boolean contract) {
	return contract ? (getPreferredValue() - getMinimumValue()) :
	(getMaximumValue() - getPreferredValue());
	}

	/pp/ double getStrain() {
	double delta = (getValue() - getPreferredValue());
	return delta/range(getValue() < getPreferredValue());
	}

	/pp/ void setStrain(double strain) {
	setValue(getPreferredValue() + (int)(strain * range(strain < 0)));
	}

	/pp/ boolean isCyclic(SpringLayout l) {
	return false;
	}

	/pp/ static abstract class AbstractSpring extends Spring {
	protected int size = UNSET;

	public int getValue() {
	return size != UNSET ? size : getPreferredValue();
	}

	public final void setValue(int size) {
	if (this.size == size) {
	return;
	}
	if (size == UNSET) {
	clear();
	} else {
	setNonClearValue(size);
	}
	}

	protected void clear() {
	size = UNSET;
	}

	protected void setNonClearValue(int size) {
	this.size = size;
	}
	}

	private static class StaticSpring extends AbstractSpring {
	protected int min;
	protected int pref;
	protected int max;

	public StaticSpring(int pref) {
	this(pref, pref, pref);
	}

	public StaticSpring(int min, int pref, int max) {
	this.min = min;
	this.pref = pref;
	this.max = max;
	}

	public String toString() {
	return "StaticSpring [" + min + ", " + pref + ", " + max + "]";
	}

	public int getMinimumValue() {
	return min;
	}

	public int getPreferredValue() {
	return pref;
	}

	public int getMaximumValue() {
	return max;
	}
	}

	private static class NegativeSpring extends Spring {
	private Spring s;

	public NegativeSpring(Spring s) {
	this.s = s;
	}

	// Note the use of max value rather than minimum value here.
	// See the opening preamble on arithmetic with springs.

	public int getMinimumValue() {
	return -s.getMaximumValue();
	}

	public int getPreferredValue() {
	return -s.getPreferredValue();
	}

	public int getMaximumValue() {
	return -s.getMinimumValue();
	}

	public int getValue() {
	return -s.getValue();
	}

	public void setValue(int size) {
	// No need to check for UNSET as
	// Integer.MIN_VALUE == -Integer.MIN_VALUE.
	s.setValue(-size);
	}

	/pp/ boolean isCyclic(SpringLayout l) {
	return s.isCyclic(l);
	}
	}

	private static class ScaleSpring extends Spring {
	private Spring s;
	private float factor;

	private ScaleSpring(Spring s, float factor) {
	this.s = s;
	this.factor = factor;
	}

	public int getMinimumValue() {
	return Math.round((factor < 0 ? s.getMaximumValue() : s.getMinimumValue()) * factor);
	}

	public int getPreferredValue() {
	return Math.round(s.getPreferredValue() * factor);
	}

	public int getMaximumValue() {
	return Math.round((factor < 0 ? s.getMinimumValue() : s.getMaximumValue()) * factor);
	}

	public int getValue() {
	return Math.round(s.getValue() * factor);
	}

	public void setValue(int value) {
	if (value == UNSET) {
	s.setValue(UNSET);
	} else {
	s.setValue(Math.round(value / factor));
	}
	}

	/pp/ boolean isCyclic(SpringLayout l) {
	return s.isCyclic(l);
	}
	}

	/pp/ static class WidthSpring extends AbstractSpring {
	/pp/ Component c;

	public WidthSpring(Component c) {
	this.c = c;
	}

	public int getMinimumValue() {
	return c.getMinimumSize().width;
	}

	public int getPreferredValue() {
	return c.getPreferredSize().width;
	}

	public int getMaximumValue() {
	// We will be doing arithmetic with the results of this call,
	// so if a returned value is Integer.MAX_VALUE we will get
	// arithmetic overflow. Truncate such values.
	return Math.min(Short.MAX_VALUE, c.getMaximumSize().width);
	}
	}

	/pp/ static class HeightSpring extends AbstractSpring {
	/pp/ Component c;

	public HeightSpring(Component c) {
	this.c = c;
	}

	public int getMinimumValue() {
	return c.getMinimumSize().height;
	}

	public int getPreferredValue() {
	return c.getPreferredSize().height;
	}

	public int getMaximumValue() {
	return Math.min(Short.MAX_VALUE, c.getMaximumSize().height);
	}
	}

	/pp/ static abstract class SpringMap extends Spring {
	private Spring s;

	public SpringMap(Spring s) {
	this.s = s;
	}

	protected abstract int map(int i);

	protected abstract int inv(int i);

	public int getMinimumValue() {
	return map(s.getMinimumValue());
	}

	public int getPreferredValue() {
	return map(s.getPreferredValue());
	}

	public int getMaximumValue() {
	return Math.min(Short.MAX_VALUE, map(s.getMaximumValue()));
	}

	public int getValue() {
	return map(s.getValue());
	}

	public void setValue(int value) {
	if (value == UNSET) {
	s.setValue(UNSET);
	} else {
	s.setValue(inv(value));
	}
	}

	/pp/ boolean isCyclic(SpringLayout l) {
	return s.isCyclic(l);
	}
	}

	// Use the instance variables of the StaticSpring superclass to
	// cache values that have already been calculated.
	/pp/ static abstract class CompoundSpring extends StaticSpring {
	protected Spring s1;
	protected Spring s2;

	public CompoundSpring(Spring s1, Spring s2) {
	super(UNSET);
	this.s1 = s1;
	this.s2 = s2;
	}

	public String toString() {
	return "CompoundSpring of " + s1 + " and " + s2;
	}

	protected void clear() {
	super.clear();
	min = pref = max = UNSET;
	s1.setValue(UNSET);
	s2.setValue(UNSET);
	}

	protected abstract int op(int x, int y);

	public int getMinimumValue() {
	if (min == UNSET) {
	min = op(s1.getMinimumValue(), s2.getMinimumValue());
	}
	return min;
	}

	public int getPreferredValue() {
	if (pref == UNSET) {
	pref = op(s1.getPreferredValue(), s2.getPreferredValue());
	}
	return pref;
	}

	public int getMaximumValue() {
	if (max == UNSET) {
	max = op(s1.getMaximumValue(), s2.getMaximumValue());
	}
	return max;
	}

	public int getValue() {
	if (size == UNSET) {
	size = op(s1.getValue(), s2.getValue());
	}
	return size;
	}

	/pp/ boolean isCyclic(SpringLayout l) {
	return l.isCyclic(s1) \|\| l.isCyclic(s2);
	}
	};

	private static class SumSpring extends CompoundSpring {
	public SumSpring(Spring s1, Spring s2) {
	super(s1, s2);
	}

	protected int op(int x, int y) {
	return x + y;
	}

	protected void setNonClearValue(int size) {
	super.setNonClearValue(size);
	s1.setStrain(this.getStrain());
	s2.setValue(size - s1.getValue());
	}
	}

	private static class MaxSpring extends CompoundSpring {

	public MaxSpring(Spring s1, Spring s2) {
	super(s1, s2);
	}

	protected int op(int x, int y) {
	return Math.max(x, y);
	}

	protected void setNonClearValue(int size) {
	super.setNonClearValue(size);
	s1.setValue(size);
	s2.setValue(size);
	}
	}

	/**
	* Returns a strut -- a spring whose <em>minimum</em>, <em>preferred</em>, and
	* <em>maximum</em> values each have the value <code>pref</code>.
	*
	* @param pref the <em>minimum</em>, <em>preferred</em>, and
	* <em>maximum</em> values of the new spring
	* @return a spring whose <em>minimum</em>, <em>preferred</em>, and
	* <em>maximum</em> values each have the value <code>pref</code>
	*
	* @see Spring
	*/
	public static Spring constant(int pref) {
	return constant(pref, pref, pref);
	}

	/**
	* Returns a spring whose <em>minimum</em>, <em>preferred</em>, and
	* <em>maximum</em> values have the values: <code>min</code>, <code>pref</code>,
	* and <code>max</code> respectively.
	*
	* @param min the <em>minimum</em> value of the new spring
	* @param pref the <em>preferred</em> value of the new spring
	* @param max the <em>maximum</em> value of the new spring
	* @return a spring whose <em>minimum</em>, <em>preferred</em>, and
	* <em>maximum</em> values have the values: <code>min</code>, <code>pref</code>,
	* and <code>max</code> respectively
	*
	* @see Spring
	*/
	public static Spring constant(int min, int pref, int max) {
	return new StaticSpring(min, pref, max);
	}


	/**
	* Returns <code>-s</code>: a spring running in the opposite direction to <code>s</code>.
	*
	* @return <code>-s</code>: a spring running in the opposite direction to <code>s</code>
	*
	* @see Spring
	*/
	public static Spring minus(Spring s) {
	return new NegativeSpring(s);
	}

	/**
	* Returns <code>s1+s2</code>: a spring representing <code>s1</code> and <code>s2</code>
	* in series. In a sum, <code>s3</code>, of two springs, <code>s1</code> and <code>s2</code>,
	* the <em>strains</em> of <code>s1</code>, <code>s2</code>, and <code>s3</code> are maintained
	* at the same level (to within the precision implied by their integer <em>value</em>s).
	* The strain of a spring in compression is:
	* <pre>
	* value - pref
	* ------------
	* pref - min
	* </pre>
	* and the strain of a spring in tension is:
	* <pre>
	* value - pref
	* ------------
	* max - pref
	* </pre>
	* When <code>setValue</code> is called on the sum spring, <code>s3</code>, the strain
	* in <code>s3</code> is calculated using one of the formulas above. Once the strain of
	* the sum is known, the <em>value</em>s of <code>s1</code> and <code>s2</code> 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 <em>value</em>s of <code>s1</code> and <code>s2</code> is exactly equal to
	* the <em>value</em> of <code>s3</code>.
	*
	* @return <code>s1+s2</code>: a spring representing <code>s1</code> and <code>s2</code> in series
	*
	* @see Spring
	*/
	public static Spring sum(Spring s1, Spring s2) {
	return new SumSpring(s1, s2);
	}

	/**
	* Returns <code>max(s1, s2)</code>: a spring whose value is always greater than (or equal to)
	* the values of both <code>s1</code> and <code>s2</code>.
	*
	* @return <code>max(s1, s2)</code>: a spring whose value is always greater than (or equal to)
	* the values of both <code>s1</code> and <code>s2</code>
	* @see Spring
	*/
	public static Spring max(Spring s1, Spring s2) {
	return new MaxSpring(s1, s2);
	}

	// Remove these, they're not used often and can be created using minus -
	// as per these implementations.

	/pp/ static Spring difference(Spring s1, Spring s2) {
	return sum(s1, minus(s2));
	}

	/*
	public static Spring min(Spring s1, Spring s2) {
	return minus(max(minus(s1), minus(s2)));
	}
	*/

	/**
	* Returns a spring whose <em>minimum</em>, <em>preferred</em>, <em>maximum</em>
	* and <em>value</em> properties are each multiples of the properties of the
	* argument spring, <code>s</code>. Minimum and maximum properties are
	* swapped when <code>factor</code> is negative (in accordance with the
	* rules of interval arithmetic).
	* <p>
	* 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.
	*
	* @param s the spring to scale
	* @param factor amount to scale by.
	* @return a spring whose properties are those of the input spring <code>s</code>
	* multiplied by <code>factor</code>
	* @throws NullPointerException if <code>s</code> is null
	* @since 1.5
	*/
	public static Spring scale(Spring s, float factor) {
	checkArg(s);
	return new ScaleSpring(s, factor);
	}

	/**
	* Returns a spring whose <em>minimum</em>, <em>preferred</em>, <em>maximum</em>
	* and <em>value</em> properties are defined by the widths of the <em>minimumSize</em>,
	* <em>preferredSize</em>, <em>maximumSize</em> and <em>size</em> 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.
	*
	* @param c Component used for calculating size
	* @return a spring whose properties are defined by the horizontal component
	* of the component's size methods.
	* @throws NullPointerException if <code>c</code> is null
	* @since 1.5
	*/
	public static Spring width(Component c) {
	checkArg(c);
	return new WidthSpring(c);
	}

	/**
	* Returns a spring whose <em>minimum</em>, <em>preferred</em>, <em>maximum</em>
	* and <em>value</em> properties are defined by the heights of the <em>minimumSize</em>,
	* <em>preferredSize</em>, <em>maximumSize</em> and <em>size</em> 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.
	*
	* @param c Component used for calculating size
	* @return a spring whose properties are defined by the vertical component
	* of the component's size methods.
	* @throws NullPointerException if <code>c</code> is null
	* @since 1.5
	*/
	public static Spring height(Component c) {
	checkArg(c);
	return new HeightSpring(c);
	}


	/**
	* If <code>s</code> is null, this throws an NullPointerException.
	*/
	private static void checkArg(Object s) {
	if (s == null) {
	throw new NullPointerException("Argument must not be null");
	}
	}
	}

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