文章目錄

• 一、拷貝簡介
• • 1.1 引用拷貝
  • 1.2 對象拷貝
• 二、淺拷貝
• • 2.1 定義
• 三、深拷貝
• • 3.1 定義

一、拷貝簡介

1.1 引用拷貝

創建一個指向對象的引用變量的拷貝

public class DemoCopy {public static void main(String[] args) {// 1. 引用拷貝：創建一個指向對象的引用變量的拷貝TempUser tempUser = new TempUser("張三",18);TempUser otherTempUser = tempUser;System.out.println(tempUser);System.out.println(otherTempUser);} }class TempUser{private String name;private int age;public String getName(){return name;}public void setName(String name){this.name = name;}public int getAge(){return age;}public void setAge(int age){this.age = age;}public TempUser(String name,int age){this.name = name;this.age = age;} }

輸出結果

com.TempUser@7ba4f24f com.TempUser@7ba4f24f

結果分析

地址值相同，說明是同一對象

tempUser 和 otherTempUser 只是引用

都指向了一個相同的對象，就叫做**引用拷貝

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1.2 對象拷貝

public class DemoCopy {public static void main(String[] args) throws CloneNotSupportedException{// 對象拷貝TempUser tempUser = new TempUser("李四",18);TempUser otherTempUser = (TempUser) tempUser1.clone();System.out.println(tempUser);System.out.println(otherTempUser);} }class TempUser implements Cloneable {private String name;private int age;public String getName(){return name;}public void setName(String name){this.name = name;}public int getAge(){return age;}public void setAge(int age){this.age = age;}public TempUser(String name,int age){this.name = name;this.age = age;}// 重寫Clone方法，將訪問權限修改為publicpublic Object clone() throws CloneNotSupportedException {Object object = super.clone();return object;} }

輸出結果

com.TempUser@3b9a45b3 com.TempUser@7699a589

結果分析

地址不同，說明創建了新的對象

不是把原對象的地址賦給了一個新的引用變量,這就叫做對象拷貝

#mermaid-svg-VA7niekqAOtOgXJQ {font-family:"trebuchet ms",verdana,arial,sans-serif;font-size:16px;fill:#333;}#mermaid-svg-VA7niekqAOtOgXJQ .error-icon{fill:#552222;}#mermaid-svg-VA7niekqAOtOgXJQ .error-text{fill:#552222;stroke:#552222;}#mermaid-svg-VA7niekqAOtOgXJQ .edge-thickness-normal{stroke-width:2px;}#mermaid-svg-VA7niekqAOtOgXJQ .edge-thickness-thick{stroke-width:3.5px;}#mermaid-svg-VA7niekqAOtOgXJQ .edge-pattern-solid{stroke-dasharray:0;}#mermaid-svg-VA7niekqAOtOgXJQ .edge-pattern-dashed{stroke-dasharray:3;}#mermaid-svg-VA7niekqAOtOgXJQ .edge-pattern-dotted{stroke-dasharray:2;}#mermaid-svg-VA7niekqAOtOgXJQ .marker{fill:#333333;stroke:#333333;}#mermaid-svg-VA7niekqAOtOgXJQ .marker.cross{stroke:#333333;}#mermaid-svg-VA7niekqAOtOgXJQ svg{font-family:"trebuchet ms",verdana,arial,sans-serif;font-size:16px;}#mermaid-svg-VA7niekqAOtOgXJQ .label{font-family:"trebuchet ms",verdana,arial,sans-serif;color:#333;}#mermaid-svg-VA7niekqAOtOgXJQ .cluster-label text{fill:#333;}#mermaid-svg-VA7niekqAOtOgXJQ .cluster-label span{color:#333;}#mermaid-svg-VA7niekqAOtOgXJQ .label text,#mermaid-svg-VA7niekqAOtOgXJQ span{fill:#333;color:#333;}#mermaid-svg-VA7niekqAOtOgXJQ .node rect,#mermaid-svg-VA7niekqAOtOgXJQ .node circle,#mermaid-svg-VA7niekqAOtOgXJQ .node ellipse,#mermaid-svg-VA7niekqAOtOgXJQ .node polygon,#mermaid-svg-VA7niekqAOtOgXJQ .node path{fill:#ECECFF;stroke:#9370DB;stroke-width:1px;}#mermaid-svg-VA7niekqAOtOgXJQ .node .label{text-align:center;}#mermaid-svg-VA7niekqAOtOgXJQ .node.clickable{cursor:pointer;}#mermaid-svg-VA7niekqAOtOgXJQ .arrowheadPath{fill:#333333;}#mermaid-svg-VA7niekqAOtOgXJQ .edgePath .path{stroke:#333333;stroke-width:2.0px;}#mermaid-svg-VA7niekqAOtOgXJQ .flowchart-link{stroke:#333333;fill:none;}#mermaid-svg-VA7niekqAOtOgXJQ .edgeLabel{background-color:#e8e8e8;text-align:center;}#mermaid-svg-VA7niekqAOtOgXJQ .edgeLabel rect{opacity:0.5;background-color:#e8e8e8;fill:#e8e8e8;}#mermaid-svg-VA7niekqAOtOgXJQ .cluster rect{fill:#ffffde;stroke:#aaaa33;stroke-width:1px;}#mermaid-svg-VA7niekqAOtOgXJQ .cluster text{fill:#333;}#mermaid-svg-VA7niekqAOtOgXJQ .cluster span{color:#333;}#mermaid-svg-VA7niekqAOtOgXJQ div.mermaidTooltip{position:absolute;text-align:center;max-width:200px;padding:2px;font-family:"trebuchet ms",verdana,arial,sans-serif;font-size:12px;background:hsl(80, 100%, 96.2745098039%);border:1px solid #aaaa33;border-radius:2px;pointer-events:none;z-index:100;}#mermaid-svg-VA7niekqAOtOgXJQ :root{--mermaid-font-family:"trebuchet ms",verdana,arial,sans-serif;} tempUser 李四,18 otherTempUser 李四,18

二、淺拷貝

2.1 定義

被復制對象的所有變量都含有與原來的對象相同的值，而所有的對其他對象的引用仍然指向原來的對象

即對象的淺拷貝會對主對象進行拷貝，但不會復制主對象里面的對象

里面的對象: 會在原來的對象和它的副本之間共享

簡而言之，淺拷貝僅僅復制所考慮的對象，而不復制它所引用的對象

淺拷貝只是增加了一個指針指向已存在的內存地址

public class DemoCopy {public static void main(String[] args) throws CloneNotSupportedException{// 淺拷貝Address address = new Address();address.setCountry("大陸");address.setProvince("天斗");TempUser tempUser2 = new TempUser();tempUser2.setName("王五");tempUser2.setAge(20);tempUser2.setAddress(address);TempUser tempUser3 = (TempUser) tempUser2.clone();System.out.println(tempUser2.getName() + " | " + tempUser2.getAge() + " | " + tempUser2.getAddress().getCountry() + " | " + tempUser2.getAddress().getProvince());System.out.println(tempUser3.getName() + " | " + tempUser3.getAge() + " | " + tempUser3.getAddress().getCountry() + " | " + tempUser3.getAddress().getProvince());System.out.println("------修改地址信息后------");address.setCountry("蒼穹");address.setProvince("烏坦");System.out.println(tempUser2.getName() + " | " + tempUser2.getAge() + " | " + tempUser2.getAddress().getCountry() + " | " + tempUser2.getAddress().getProvince());System.out.println(tempUser3.getName() + " | " + tempUser3.getAge() + " | " + tempUser3.getAddress().getCountry() + " | " + tempUser3.getAddress().getProvince());} }class TempUser implements Cloneable {private String name;private int age;private Address address;public String getName(){return name;}public void setName(String name){this.name = name;}public int getAge(){return age;}public void setAge(int age){this.age = age;}public Address getAddress(){return address;}public void setAddress(Address address){this.address = address;}public TempUser(){}public TempUser(String name,int age){this.name = name;this.age = age;}public TempUser(String name,int age,Address address){this.name = name;this.age = age;this.address = address;}// 重寫Clone方法，將訪問權限修改為publicpublic Object clone() throws CloneNotSupportedException {Object object = super.clone();return object;} }class Address implements Cloneable{private String country;private String province;public String getCountry(){return country;}public void setCountry(String country){this.country = country;}public String getProvince(){return province;}public void setProvince(String province){this.province = province;}public Address(){}public Address(String country,String province){this.country = country;this.province = province;} }

輸出結果

王五 | 20 | 大陸 | 天斗 王五 | 20 | 大陸 | 天斗 ------修改地址信息后------ 王五 | 20 | 蒼穹 | 烏坦 王五 | 20 | 蒼穹 | 烏坦

結果分析

兩個引用 tempUser2 和 tempUser3 指向不同的兩個對象

兩個引用 tempUser2 和 tempUser3 中的兩個address引用指向的是同一個對象，所以說明是淺拷貝

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三、深拷貝

3.1 定義

深拷貝是一整個獨立的對象拷貝，深拷貝會拷貝所有的屬性,并拷貝屬性指向的動態分配的內存

當對象和它所引用的對象一起拷貝時即發生深拷貝

深拷貝相比于淺拷貝速度較慢并且花銷較大

簡而言之，深拷貝把要復制的對象所引用的對象都復制了一遍

深拷貝是增加了一個指針并且申請了一個新的內存，使這個增加的指針指向這個新的內存

使用深拷貝的情況下，釋放內存的時候不會因為出現淺拷貝時釋放同一個內存的錯誤

public class DemoCopy {public static void main(String[] args) throws CloneNotSupportedException{// 深拷貝Address address1 = new Address();address1.setCountry("遮天");address1.setProvince("天庭");TempUser tempUser4 = new TempUser();tempUser4.setName("趙六");tempUser4.setAge(18);tempUser4.setAddress(address1);TempUser tempUser5 = (TempUser) tempUser4.clone();System.out.println(tempUser4.getName() + " | " + tempUser4.getAge() + " | " + tempUser4.getAddress().getCountry() + " | " + tempUser4.getAddress().getProvince());System.out.println(tempUser5.getName() + " | " + tempUser5.getAge() + " | " + tempUser5.getAddress().getCountry() + " | " + tempUser5.getAddress().getProvince());System.out.println("------修改地址信息后------");address1.setCountry("完美");address1.setProvince("世界");System.out.println(tempUser4.getName() + " | " + tempUser4.getAge() + " | " + tempUser4.getAddress().getCountry() + " | " + tempUser4.getAddress().getProvince());System.out.println(tempUser5.getName() + " | " + tempUser5.getAge() + " | " + tempUser5.getAddress().getCountry() + " | " + tempUser5.getAddress().getProvince());} }class TempUser implements Cloneable {private String name;private int age;private Address address;public String getName(){return name;}public void setName(String name){this.name = name;}public int getAge(){return age;}public void setAge(int age){this.age = age;}public Address getAddress(){return address;}public void setAddress(Address address){this.address = address;}public TempUser(){}public TempUser(String name,int age){this.name = name;this.age = age;}public TempUser(String name,int age,Address address){this.name = name;this.age = age;this.address = address;}// 重寫Clone方法，將訪問權限修改為publicpublic Object clone() throws CloneNotSupportedException {// 淺復制/*Object object = super.clone();return object;*/// 深復制TempUser tempUser = (TempUser) super.clone();tempUser.setAddress((Address) tempUser.getAddress().clone());return tempUser;} }class Address implements Cloneable{private String country;private String province;public String getCountry(){return country;}public void setCountry(String country){this.country = country;}public String getProvince(){return province;}public void setProvince(String province){this.province = province;}public Address(){}public Address(String country,String province){this.country = country;this.province = province;}public Object clone() throws CloneNotSupportedException {// 淺復制Object object = super.clone();return object;} }

輸出結果

趙六 | 18 | 遮天 | 天庭 趙六 | 18 | 遮天 | 天庭 ------修改地址信息后------ 趙六 | 18 | 完美 | 世界 趙六 | 18 | 遮天 | 天庭

結果分析

兩個引用 tempUser4 和 tempUser5 指向不同的兩個對象

兩個引用 tempUser4 和 tempUser5 中的兩個 address1 引用指向的是兩個對象

對 address1 對象的修改只能影響 tempUser4 對象,所以說是深拷貝

總結

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