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iluwatariluwatar
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Improved encapsulation of the Memento pattern by moving the
StarMementoInternal class to inner class of Star.
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7 files changed

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‎README.md‎

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Original file line numberDiff line numberDiff line change
@@ -353,7 +353,7 @@ A programming idiom is a means of expressing a recurring construct in one or mor
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## <a name="memento">Memento</a> [&#8593;](#list-of-design-patterns)
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**Intent:** Without violating encapsulation, capture and externalize an object's internal state so that the object can be restored to this state later.
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![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/memento/etc/memento_1.png "Memento")
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![alt text](https://github.com/iluwatar/java-design-patterns/blob/master/memento/etc/memento.png "Memento")
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**Applicability:** Use the Memento pattern when
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* a snapshot of an object's state must be saved so that it can be restored to that state later, and

‎memento/etc/memento.jpg‎

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‎memento/etc/memento.png‎

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‎memento/etc/test.ucls‎ renamed to ‎memento/etc/memento.ucls‎

Lines changed: 30 additions & 30 deletions
Original file line numberDiff line numberDiff line change
@@ -1,65 +1,65 @@
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<?xml version="1.0" encoding="UTF-8"?>
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<class-diagram version="1.1.7" icons="true" always-add-relationships="false" generalizations="true" realizations="true"
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associations="true" dependencies="false" nesting-relationships="true">
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<class-diagram version="1.1.8" icons="true" automaticImage="PNG" always-add-relationships="false" generalizations="true"
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realizations="true" associations="true" dependencies="false" nesting-relationships="true">
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<class id="1" language="java" name="com.iluwatar.Star" project="memento"
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file="/memento/src/main/java/com/iluwatar/Star.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="-1" width="-1" x="383" y="159"/>
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<position height="-1" width="-1" x="301" y="385"/>
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<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
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sort-features="false" accessors="true" visibility="true">
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<attributes public="true" package="true" protected="true" private="true" static="true"/>
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<operations public="true" package="true" protected="true" private="true" static="true"/>
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</display>
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</class>
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<class id="2" language="java" name="com.iluwatar.StarMementoInternal" project="memento"
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file="/memento/src/main/java/com/iluwatar/StarMementoInternal.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="-1" width="-1" x="697" y="141"/>
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<enumeration id="2" language="java" name="com.iluwatar.StarType" project="memento"
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file="/memento/src/main/java/com/iluwatar/StarType.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="-1" width="-1" x="301" y="911"/>
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<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
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sort-features="false" accessors="true" visibility="true">
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<attributes public="true" package="true" protected="true" private="true" static="true"/>
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<operations public="true" package="true" protected="true" private="true" static="true"/>
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</display>
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</class>
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<enumeration id="3" language="java" name="com.iluwatar.StarType" project="memento"
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file="/memento/src/main/java/com/iluwatar/StarType.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="-1" width="-1" x="533" y="429"/>
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</enumeration>
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<interface id="3" language="java" name="com.iluwatar.StarMemento" project="memento"
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file="/memento/src/main/java/com/iluwatar/StarMemento.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="-1" width="-1" x="103" y="830"/>
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<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
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sort-features="false" accessors="true" visibility="true">
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<attributes public="true" package="true" protected="true" private="true" static="true"/>
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<operations public="true" package="true" protected="true" private="true" static="true"/>
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</display>
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</enumeration>
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<interface id="4" language="java" name="com.iluwatar.StarMemento" project="memento"
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file="/memento/src/main/java/com/iluwatar/StarMemento.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="-1" width="-1" x="536" y="-17"/>
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</interface>
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<class id="4" language="java" name="com.iluwatar.Star.StarMementoInternal" project="memento"
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file="/memento/src/main/java/com/iluwatar/Star.java" binary="false" corner="BOTTOM_RIGHT">
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<position height="-1" width="-1" x="103" y="639"/>
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<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
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sort-features="false" accessors="true" visibility="true">
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<attributes public="true" package="true" protected="true" private="true" static="true"/>
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<operations public="true" package="true" protected="true" private="true" static="true"/>
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</display>
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</interface>
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<dependency id="5">
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<end type="SOURCE" refId="1"/>
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<end type="TARGET" refId="4"/>
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</dependency>
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<association id="6">
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</class>
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<association id="5">
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<end type="SOURCE" refId="1" navigable="false">
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<attribute id="7" name="type"/>
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<multiplicity id="8" minimum="0" maximum="1"/>
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<attribute id="6" name="type"/>
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<multiplicity id="7" minimum="0" maximum="1"/>
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</end>
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<end type="TARGET" refId="3" navigable="true"/>
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<end type="TARGET" refId="2" navigable="true"/>
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<display labels="true" multiplicity="true"/>
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</association>
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<association id="9">
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<end type="SOURCE" refId="2" navigable="false">
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<attribute id="10" name="type"/>
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<multiplicity id="11" minimum="0" maximum="1"/>
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<association id="8">
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<end type="SOURCE" refId="4" navigable="false">
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<attribute id="9" name="type"/>
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<multiplicity id="10" minimum="0" maximum="1"/>
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</end>
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<end type="TARGET" refId="3" navigable="true"/>
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<end type="TARGET" refId="2" navigable="true"/>
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<display labels="true" multiplicity="true"/>
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</association>
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<realization id="12">
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<end type="SOURCE" refId="2"/>
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<nesting id="11">
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<end type="SOURCE" refId="1"/>
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<end type="TARGET" refId="4"/>
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</nesting>
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<realization id="12">
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<end type="SOURCE" refId="4"/>
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<end type="TARGET" refId="3"/>
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</realization>
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<classifier-display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
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sort-features="false" accessors="true" visibility="true">

‎memento/etc/memento_1.png‎

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‎memento/src/main/java/com/iluwatar/Star.java‎

Lines changed: 105 additions & 69 deletions
Original file line numberDiff line numberDiff line change
@@ -1,69 +1,105 @@
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package com.iluwatar;
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/**
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*
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* Star uses "mementos" to store and restore state.
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*
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*/
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public class Star {
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private StarType type;
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private int ageYears;
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private int massTons;
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public Star(StarType startType, int startAge, int startMass) {
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this.type = startType;
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this.ageYears = startAge;
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this.massTons = startMass;
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}
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public void timePasses() {
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ageYears *= 2;
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massTons *= 8;
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switch (type) {
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case RED_GIANT:
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type = StarType.WHITE_DWARF;
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break;
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case SUN:
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type = StarType.RED_GIANT;
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break;
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case SUPERNOVA:
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type = StarType.DEAD;
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break;
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case WHITE_DWARF:
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type = StarType.SUPERNOVA;
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break;
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case DEAD:
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ageYears *= 2;
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massTons = 0;
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break;
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default:
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break;
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}
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}
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StarMemento getMemento() {
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StarMementoInternal state = new StarMementoInternal();
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state.setAgeYears(ageYears);
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state.setMassTons(massTons);
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state.setType(type);
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return state;
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}
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void setMemento(StarMemento memento) {
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StarMementoInternal state = (StarMementoInternal) memento;
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this.type = state.getType();
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this.ageYears = state.getAgeYears();
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this.massTons = state.getMassTons();
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}
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@Override
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public String toString() {
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return String.format("%s age: %d years mass: %d tons", type.toString(),
67-
ageYears, massTons);
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}
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}
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package com.iluwatar;
2+
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/**
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*
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* Star uses "mementos" to store and restore state.
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*
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*/
8+
public class Star {
9+
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private StarType type;
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private int ageYears;
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private int massTons;
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public Star(StarType startType, int startAge, int startMass) {
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this.type = startType;
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this.ageYears = startAge;
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this.massTons = startMass;
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}
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public void timePasses() {
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ageYears *= 2;
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massTons *= 8;
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switch (type) {
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case RED_GIANT:
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type = StarType.WHITE_DWARF;
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break;
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case SUN:
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type = StarType.RED_GIANT;
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break;
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case SUPERNOVA:
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type = StarType.DEAD;
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break;
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case WHITE_DWARF:
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type = StarType.SUPERNOVA;
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break;
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case DEAD:
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ageYears *= 2;
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massTons = 0;
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break;
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default:
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break;
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}
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}
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StarMemento getMemento() {
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StarMementoInternal state = new StarMementoInternal();
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state.setAgeYears(ageYears);
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state.setMassTons(massTons);
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state.setType(type);
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return state;
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}
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void setMemento(StarMemento memento) {
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StarMementoInternal state = (StarMementoInternal) memento;
58+
this.type = state.getType();
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this.ageYears = state.getAgeYears();
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this.massTons = state.getMassTons();
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}
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@Override
65+
public String toString() {
66+
return String.format("%s age: %d years mass: %d tons", type.toString(),
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ageYears, massTons);
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}
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/**
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*
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* StarMemento implementation
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*
74+
*/
75+
private static class StarMementoInternal implements StarMemento {
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private StarType type;
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private int ageYears;
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private int massTons;
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public StarType getType() {
82+
return type;
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}
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85+
public void setType(StarType type) {
86+
this.type = type;
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}
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89+
public int getAgeYears() {
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return ageYears;
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}
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93+
public void setAgeYears(int ageYears) {
94+
this.ageYears = ageYears;
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}
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public int getMassTons() {
98+
return massTons;
99+
}
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101+
public void setMassTons(int massTons) {
102+
this.massTons = massTons;
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}
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}
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}

‎memento/src/main/java/com/iluwatar/StarMementoInternal.java‎

Lines changed: 0 additions & 37 deletions
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