java 中的构造方法及一个标准的类

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构造方法

构造方法–是专门用来创建对象的方法，当我们通过关键字 new 来创建对象时，其实是在调用构造方法。
格式；
public class="tags" href="/tags/Lei.html" title=类>类名称（参数class="tags" href="/tags/Lei.html" title=类>类型参数名称）{
方法体
}
this（）是调用本class="tags" href="/tags/Lei.html" title=类>类不带参构造方法；
super（）是调用父class="tags" href="/tags/Lei.html" title=类>类不带参的构造方法；
注意事项；
1.构造方法的名称必须和所在的class="tags" href="/tags/Lei.html" title=类>类名称完全一样，就连大小写也要一样。

class="prism language-class="tags" href="/tags/JAVA.html" title=java>java">class="token keyword">public class="token keyword">class class="token class-name">Aclass="token punctuation">{
		class="token keyword">int iclass="token operator">=class="token number">0class="token punctuation">;
		class="token keyword">public class="token function">Aclass="token punctuation">(class="token punctuation">)class="token punctuation">{
			iclass="token operator">=class="token number">2class="token punctuation">;
		class="token punctuation">}
		class="token keyword">public class="token function">Aclass="token punctuation">(class="token keyword">int iclass="token punctuation">)class="token punctuation">{
			class="token keyword">thisclass="token punctuation">.iclass="token operator">=iclass="token punctuation">;
		class="token punctuation">}
	class="token punctuation">}

2.构造方法不要写返回值class="tags" href="/tags/Lei.html" title=类>类型，连== void == 都不要写。

构造方法的用途

构造方法的用途就是用来创建对象。（初始化对象）当我们通过关键字 new 来创建对象时，其实是在调用构造方法。
注意；
3.构造方法不能有return一个具体的返回值。
4.如果没有编写任何构造方法，那么编译器将会默认真赠送一个构造方法，没有参数，方法体什么事情都不用做。
举例；
public student（）{
}
5.一旦编写了一个至少一个构造方法，那么编译器将不再赠送。
6.构造方法也是可以重载的。（重载–方法名称相同，参数列表不同）

class="prism language-class="tags" href="/tags/JAVA.html" title=java>java">class="token keyword">public class="token keyword">class class="token class-name">Aclass="token punctuation">{
	class="token keyword">private class="token keyword">int ageclass="token punctuation">;
	class="token keyword">private String nameclass="token punctuation">;
	class="token keyword">public class="token function">Aclass="token punctuation">(class="token keyword">int ageclass="token punctuation">,String nameclass="token punctuation">)class="token punctuation">{
		class="token keyword">thisclass="token punctuation">.ageclass="token operator">=ageclass="token punctuation">;
		class="token keyword">thisclass="token punctuation">.nameclass="token operator">=nameclass="token punctuation">;
	class="token punctuation">}
	class="token keyword">public class="token function">Aclass="token punctuation">(class="token keyword">int ageclass="token punctuation">)class="token punctuation">{
		class="token keyword">thisclass="token punctuation">(ageclass="token punctuation">,class="token string">"周杰伦"class="token punctuation">)class="token punctuation">;class="token comment">//调用 A(int age,String name)构造方法
	class="token punctuation">}
	class="token keyword">public class="token function">Aclass="token punctuation">(class="token punctuation">)class="token punctuation">{
		class="token keyword">thisclass="token punctuation">(class="token number">1class="token punctuation">)class="token punctuation">;class="token comment">//调用 A(int age)构造方法
	class="token punctuation">}
	class="token keyword">public class="token keyword">void class="token function">setNameclass="token punctuation">(String nameclass="token punctuation">) class="token punctuation">{class="token keyword">thisclass="token punctuation">.nameclass="token operator">=nameclass="token punctuation">;class="token punctuation">}
	class="token keyword">public String class="token function">getNameclass="token punctuation">(class="token punctuation">) class="token punctuation">{class="token keyword">return nameclass="token punctuation">;class="token punctuation">}
	class="token keyword">public class="token keyword">void class="token function">setAgeclass="token punctuation">(class="token keyword">int ageclass="token punctuation">) class="token punctuation">{class="token keyword">thisclass="token punctuation">.ageclass="token operator">=ageclass="token punctuation">;class="token punctuation">}
	class="token keyword">public class="token keyword">int class="token function">getAgeclass="token punctuation">(class="token punctuation">) class="token punctuation">{class="token keyword">return ageclass="token punctuation">;class="token punctuation">}
class="token punctuation">}

class="prism language-class="tags" href="/tags/JAVA.html" title=java>java">A aclass="token operator">=class="token keyword">new class="token class-name">Aclass="token punctuation">(class="token number">20class="token punctuation">,class="token string">"邓紫棋"class="token punctuation">)class="token punctuation">;
A bclass="token operator">=class="token keyword">new class="token class-name">Aclass="token punctuation">(class="token number">20class="token punctuation">)class="token punctuation">;
A cclass="token operator">=class="token keyword">new class="token class-name">Aclass="token punctuation">(class="token punctuation">)class="token punctuation">;
String name class="token operator">= aclass="token punctuation">.class="token function">getNameclass="token punctuation">(class="token punctuation">)class="token punctuation">;
String name1 class="token operator">= bclass="token punctuation">.class="token function">getNameclass="token punctuation">(class="token punctuation">)class="token punctuation">;
class="token keyword">int age class="token operator">= cclass="token punctuation">.class="token function">getAgeclass="token punctuation">(class="token punctuation">)class="token punctuation">;
Systemclass="token punctuation">.outclass="token punctuation">.class="token function">printlnclass="token punctuation">(nameclass="token punctuation">)class="token punctuation">;
Systemclass="token punctuation">.outclass="token punctuation">.class="token function">printlnclass="token punctuation">(name1class="token punctuation">)class="token punctuation">;
Systemclass="token punctuation">.outclass="token punctuation">.class="token function">printlnclass="token punctuation">(ageclass="token punctuation">)class="token punctuation">;

定义一个标准的class="tags" href="/tags/Lei.html" title=类>类

一个标准的class="tags" href="/tags/Lei.html" title=类>类通常要拥有以下四个组成部分；
1.所有的成员变量都要用 private 关键词，来修饰成员变量。
2.为每一个成员变量编写一对 getter/setter 方法。
3.编写一个无参数的构造方法。
4.编写一个全参数的构造方法。
这样的一个标准的class="tags" href="/tags/Lei.html" title=类>类也叫做 class="tags" href="/tags/JAVA.html" title=java>java bean（豆）。

源代码：
Studentclass="tags" href="/tags/Lei.html" title=类>类：

class="prism language-class="tags" href="/tags/JAVA.html" title=java>java">ackage itcastclass="token punctuation">.cnclass="token punctuation">;

class="token keyword">public class="token keyword">class class="token class-name">Student class="token punctuation">{
    class="token keyword">private String nameclass="token punctuation">;  class="token comment">//姓名
    class="token keyword">private class="token keyword">int ageclass="token punctuation">;      class="token comment">//年龄

    class="token keyword">public class="token function">Studentclass="token punctuation">(String nameclass="token punctuation">, class="token keyword">int ageclass="token punctuation">) class="token punctuation">{
        class="token keyword">thisclass="token punctuation">.name class="token operator">= nameclass="token punctuation">;
        class="token keyword">thisclass="token punctuation">.age class="token operator">= ageclass="token punctuation">;
    class="token punctuation">}

    class="token keyword">public class="token function">Studentclass="token punctuation">(class="token punctuation">) class="token punctuation">{
    class="token punctuation">}

    class="token keyword">public String class="token function">getNameclass="token punctuation">(class="token punctuation">) class="token punctuation">{
        class="token keyword">return nameclass="token punctuation">;
    class="token punctuation">}

    class="token keyword">public class="token keyword">void class="token function">setNameclass="token punctuation">(String nameclass="token punctuation">) class="token punctuation">{
        class="token keyword">thisclass="token punctuation">.name class="token operator">= nameclass="token punctuation">;
    class="token punctuation">}

    class="token keyword">public class="token keyword">int class="token function">getAgeclass="token punctuation">(class="token punctuation">) class="token punctuation">{
        class="token keyword">return ageclass="token punctuation">;
    class="token punctuation">}

    class="token keyword">public class="token keyword">void class="token function">setAgeclass="token punctuation">(class="token keyword">int ageclass="token punctuation">) class="token punctuation">{
        class="token keyword">thisclass="token punctuation">.age class="token operator">= ageclass="token punctuation">;
    class="token punctuation">}
class="token punctuation">}

mainclass="tags" href="/tags/Lei.html" title=类>类；

class="prism language-class="tags" href="/tags/JAVA.html" title=java>java">class="token keyword">package itcastclass="token punctuation">.cnclass="token punctuation">;

class="token keyword">public class="token keyword">class class="token class-name">Main class="token punctuation">{
    class="token keyword">public class="token keyword">static class="token keyword">void class="token function">mainclass="token punctuation">(Stringclass="token punctuation">[class="token punctuation">] argsclass="token punctuation">) class="token punctuation">{
        Student stu1 class="token operator">= class="token keyword">new class="token class-name">Studentclass="token punctuation">(class="token punctuation">)class="token punctuation">;
        stu1class="token punctuation">.class="token function">setNameclass="token punctuation">(class="token string">"Tom"class="token punctuation">)class="token punctuation">;
        stu1class="token punctuation">.class="token function">setAgeclass="token punctuation">(class="token number">19class="token punctuation">)class="token punctuation">;
        Systemclass="token punctuation">.outclass="token punctuation">.class="token function">printlnclass="token punctuation">(class="token string">"姓名："class="token operator">+stu1class="token punctuation">.class="token function">getNameclass="token punctuation">(class="token punctuation">)class="token operator">+class="token string">"，年龄："class="token operator">+stu1class="token punctuation">.class="token function">getAgeclass="token punctuation">(class="token punctuation">)class="token punctuation">)class="token punctuation">;
        Systemclass="token punctuation">.outclass="token punctuation">.class="token function">printlnclass="token punctuation">(class="token string">"============="class="token punctuation">)class="token punctuation">;

        Student stu2 class="token operator">= class="token keyword">new class="token class-name">Studentclass="token punctuation">(class="token string">"Ben"class="token punctuation">,class="token number">20class="token punctuation">)class="token punctuation">;
        Systemclass="token punctuation">.outclass="token punctuation">.class="token function">printlnclass="token punctuation">(class="token string">"姓名："class="token operator">+stu2class="token punctuation">.class="token function">getNameclass="token punctuation">(class="token punctuation">)class="token operator">+class="token string">"，年龄："class="token operator">+stu2class="token punctuation">.class="token function">getAgeclass="token punctuation">(class="token punctuation">)class="token punctuation">)class="token punctuation">;
    class="token punctuation">}
class="token punctuation">}