我是java的新手,并试图运行一个简单的计算量的代码.代码如下:
package chapter6;
class Box {
double width;
double height;
double depth;
}
package chapter6;
public class BoxDemo {
public static void main(String[] args) {
Box myBox = new Box();
double vol;
myBox.depth = 1;
myBox.height = 2;
myBox.width = 3;
vol = myBox.depth * myBox.height * myBox.width ;
System.out.println("Volume: " + vol);
}
}
我能够从eclipse运行代码,但是当我尝试在命令提示符下运行代码时,我得到错误:
C:\Prabhjot\Java\CompleteRefence\build\classes>java BoxDemo.class
Exception in thread "main" java.lang.NoClassDefFoundError: BoxDemo/class
Caused by: java.lang.ClassNotFoundException: BoxDemo.class
at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
at …java新手,仍然在努力使用新的关键字和继承:
public class A1 {
void a_method (){
System.out.println("Inside A1 method");
}
}
public class A2 extends A1{
void a_method(){
System.out.println("Inside A2 method");
}
}
public class TestA1A2 {
public static void main(String[] args) {
A1 a1 = new A1();
A1 a2 = new A2(); //not sure if it created object of A1 or A2
A2 a3 = new A2();
a1.a_method();
a2.a_method();
a3.a_method();
}
}
我正在努力理解新关键字,如果在上面的代码中:
A1 a2 = new A2(); //not sure if it created object of A1 or …drink = 'beer'
switch(drink){
case 'beer':
case 'whiskey':
console.log('The drink is BEER or WHISKEY');
case 'juice':
console.log('The drink is JUICE');
default:
console.log('Nothing to drink');
}对于上面的代码，为什么我会在控制台中收到所有三个消息？有人可以解释一下吗？如果没有break，我期望打印案例消息和默认消息，但为什么“juice”相关消息也出现在控制台中？
我仍然是Java的新手.我的问题可能非常基本.
我有一个班级超级班,
package chapter8;
public class Box {
double width;
private double height;
private double depth;
Box(double w, double h, double d) {
width = w;
height = h;
depth = d;
}
double volume() {
return width * height * depth;
}
}
BoxWeight是Box超类的子类:
package chapter8;
public class BoxWeight extends Box {
double weight;
BoxWeight(double w, double h, double d, double m){
super(w, h, d);
weight = m;
}
}
现在我主要在DemoBoxWeight
package chapter8;
public class DemoBoxWeight {
public static …