Java 程序求一个长方体的体积，用到的知识父类之类

我直接给你写一个吧
public class ChangFangTi{
private double chang;
private double kuan;
private double gao;
public ChangFangTi(){}
public ChangFangTi(double chang,double kuan,double gao){
this.chang = chang;
this.kuan = kuan;
this.gao = gao;
}
public void setChang(double chang){
this.chang = chang;
}
public double getChang(){
return this.chang;
}
public void setKuan(double kuan){
this.kuan = kuan;
}
public double getKuan(){
return this.kuan;
}
public void setGao(double gao){
this.gao = gao;
}
public double getGao(){
return this.gao;
}
public double mianji(){
return chang * kuan * gao;
}
public static void main(String [] args){
ChangFangTi cft = new ChangFangTi(2,3,5);
System.out.println("长方体的体积是:" + cft.mianji());
}
}