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一个对象调用另外一个对象:
方法一: Teacher类public class Teacher { private String name; private String subject; public Teacher() { } public Teacher(String name,String subject){ this.name = name; this.subject = subject; } public void teach(){ System.out.println(name + " is teaching " + subject); } public static void main(String[] args){ Teacher teacher = new Teacher(); teacher.teach(); }}
Student类: (这里调用了另一个对象)
public class Student { private String name; public Student(){ } public Student(String name){ this.name = name; } public void study(){ Teacher teacher = new Teacher("jinhua","programing"); teacher.teach(); System.out.println(name +" is studying"); }}
Test类:
public class Test { public static void main(String[] args) { Student student = new Student("jack"); student.study(); }}
方法二:修改Student类和Test类,在Student类外生成另一个对象,传进study。
public class Student { private String name; public Student(){ } public Student(String name){ this.name = name; } public void study(Teacher teacher){ teacher.teach(); System.out.println(name +" is studying"); }}
public class Test { public static void main(String[] args) { Teacher teacher = new Teacher("jinhua","programing"); Student student = new Student("jack"); student.study(teacher); }}
输出结果都是:
jinhua is teaching programing jack is studying二、打jar包
1、在Teacher.java、Student.java、Test.java目录下,创建清单文件manifest.mf,文件内容一句话:Main-Class:Test。 2、终端输入命令 jar cvfn test.jar mainfest.mf Teacher.java Student.java Test.java 即会生成test.jar压缩文件 3、运行jar文件: java -jar test.jar。三、到底调用哪一个方法
父类 对象 = new 子类();Father obj = new Son();
obj对象只能调用子类继承或者复写的方法;
比如Son里有两个方法:吃饭和尿床。 obj.吃饭,调用的是子类的吃饭方法; obj.尿床,语法错误。4、匿名对象的生成及调用(在堆内存里有对象,在栈内存里没有名字)
new Student().study(); //匿名对象调用study函数.匿名对象只能用一次5、空对象(在栈内存里有名字,在堆内存里没有对象)
Student s = null; //null:空 (会导致空指针异常)转载地址:http://chani.baihongyu.com/