Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ /** * A mutable <code>double</code> wrapper. * * @see Double * @since 2.1 * @version $Id: MutableDouble.java 618693 2008-02-05 16:33:29Z sebb $ */ public class MutableDouble extends Number implements Comparable, Mutable { /** * Required for serialization support. * * @see java.io.Serializable */ private static final long serialVersionUID = 1587163916L; /** The mutable value. */ private double value; /** * Constructs a new MutableDouble with the default value of zero. */ public MutableDouble() { super(); } /** * Constructs a new MutableDouble with the specified value. * * @param value * a value. */ public MutableDouble(double value) { super(); this.value = value; } /** * Constructs a new MutableDouble with the specified value. * * @param value * a value. * @throws NullPointerException * if the object is null */ public MutableDouble(Number value) { super(); this.value = value.doubleValue(); } // ----------------------------------------------------------------------- /** * Gets the value as a Double instance. * * @return the value as a Double */ public Object getValue() { return new Double(this.value); } /** * Sets the value. * * @param value * the value to set */ public void setValue(double value) { this.value = value; } /** * Sets the value from any Number instance. * * @param value * the value to set * @throws NullPointerException * if the object is null * @throws ClassCastException * if the type is not a {@link Number} */ public void setValue(Object value) { setValue(((Number) value).doubleValue()); } // ----------------------------------------------------------------------- // shortValue and bytValue rely on Number implementation /** * Returns the value of this MutableDouble as a int. * * @return the numeric value represented by this object after conversion to * type int. */ public int intValue() { return (int) value; } /** * Returns the value of this MutableDouble as a long. * * @return the numeric value represented by this object after conversion to * type long. */ public long longValue() { return (long) value; } /** * Returns the value of this MutableDouble as a float. * * @return the numeric value represented by this object after conversion to * type float. */ public float floatValue() { return (float) value; } /** * Returns the value of this MutableDouble as a double. * * @return the numeric value represented by this object after conversion to * type double. */ public double doubleValue() { return value; } /** * Checks whether the double value is the special NaN value. * * @return true if NaN */ public boolean isNaN() { return Double.isNaN(value); } /** * Checks whether the double value is infinite. * * @return true if infinite */ public boolean isInfinite() { return Double.isInfinite(value); } // ----------------------------------------------------------------------- /** * Gets this mutable as an instance of Double. * * @return a Double instance containing the value from this mutable */ public Double toDouble() { return new Double(doubleValue()); } // ----------------------------------------------------------------------- /** * Increments the value. * * @since Commons Lang 2.2 */ public void increment() { value++; } /** * Decrements the value. * * @since Commons Lang 2.2 */ public void decrement() { value--; } // ----------------------------------------------------------------------- /** * Adds a value. * * @param operand * the value to add * * @since Commons Lang 2.2 */ public void add(double operand) { this.value += operand; } /** * Adds a value. * * @param operand * the value to add * @throws NullPointerException * if the object is null * * @since Commons Lang 2.2 */ public void add(Number operand) { this.value += operand.doubleValue(); } /** * Subtracts a value. * * @param operand * the value to add * * @since Commons Lang 2.2 */ public void subtract(double operand) { this.value -= operand; } /** * Subtracts a value. * * @param operand * the value to add * @throws NullPointerException * if the object is null * * @since Commons Lang 2.2 */ public void subtract(Number operand) { this.value -= operand.doubleValue(); } // ----------------------------------------------------------------------- /** * Compares this object against the specified object. The result is * <code>true</code> if and only if the argument is not <code>null</code> * and is a <code>Double</code> object that represents a double that has the * identical bit pattern to the bit pattern of the double represented by this * object. For this purpose, two <code>double</code> values are considered * to be the same if and only if the method * {@link Double#doubleToLongBits(double)}returns the same long value when * applied to each. * <p> * Note that in most cases, for two instances of class <code>Double</code>,<code>d1</code> * and <code>d2</code>, the value of <code>d1.equals(d2)</code> is * <code>true</code> if and only if <blockquote> * * <pre> * d1.doubleValue() == d2.doubleValue() * </pre> * * </blockquote> * <p> * also has the value <code>true</code>. However, there are two exceptions: * <ul> * <li>If <code>d1</code> and <code>d2</code> both represent * <code>Double.NaN</code>, then the <code>equals</code> method returns * <code>true</code>, even though <code>Double.NaN==Double.NaN</code> has * the value <code>false</code>. * <li>If <code>d1</code> represents <code>+0.0</code> while * <code>d2</code> represents <code>-0.0</code>, or vice versa, the * <code>equal</code> test has the value <code>false</code>, even though * <code>+0.0==-0.0</code> has the value <code>true</code>. This allows * hashtables to operate properly. * </ul> * * @param obj * the object to compare with. * @return <code>true</code> if the objects are the same; <code>false</code> * otherwise. */ public boolean equals(Object obj) { return (obj instanceof MutableDouble) && (Double.doubleToLongBits(((MutableDouble) obj).value) == Double.doubleToLongBits(value)); } /** * Returns a suitable hashcode for this mutable. * * @return a suitable hashcode */ public int hashCode() { long bits = Double.doubleToLongBits(value); return (int) (bits ^ (bits >>> 32)); } /** * Compares this mutable to another in ascending order. * * @param obj * the mutable to compare to * @return negative if this is less, zero if equal, positive if greater * @throws ClassCastException * if the argument is not a MutableDouble */ public int compareTo(Object obj) { MutableDouble other = (MutableDouble) obj; double anotherVal = other.value; return compare(value, anotherVal); } /** * Returns the String value of this mutable. * * @return the mutable value as a string */ public String toString() { return String.valueOf(value); } protected int compare(Object o1, Object o2) { if (o1 == null) { if (o2 == null) { return 0; } else { return -((Comparable) o2).compareTo(o1); } } else { return ((Comparable) o1).compareTo(o2); } } } /* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with this * work for additional information regarding copyright ownership. The ASF * licenses this file to You under the Apache License, Version 2.0 (the * "License"); you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the * License for the specific language governing permissions and limitations under * the License. */ /** * Provides mutable access to a value. * <p> * <code>Mutable</code> is used as a generic interface to the implementations * in this package. * <p> * A typical use case would be to enable a primitive or string to be passed to a * method and allow that method to effectively change the value of the * primitive/string. Another use case is to store a frequently changing * primitive in a collection (for example a total in a map) without needing to * create new Integer/Long wrapper objects. * * @author Matthew Hawthorne * @since 2.1 * @version $Id: Mutable.java 618693 2008-02-05 16:33:29Z sebb $ */ interface Mutable { /** * Gets the value of this mutable. * * @return the stored value */ Object getValue(); /** * Sets the value of this mutable. * * @param value * the value to store * @throws NullPointerException * if the object is null and null is invalid * @throws ClassCastException * if the type is invalid */ void setValue(Object value); }