本例以Box类为例，比较两种语言基本的类实例区别

Java：

package practice;

public class Box {
    public      int   length;
    private     int   height;
    protected   int   width;

    public Box(int length, int width, int height){
        this.length = length;
        this.width = width;
        this.height = height;
    }

    public void putItem(){
        System.out.println("盒子的长："+this.length);
        System.out.println("盒子的宽："+this.width);
        System.out.println("盒子的高："+this.height);
    }

    public static void main(String[] args) {
        Box box = new Box(2,2,3);
        box.putItem();
    }
}

Ruby：

class Box
  def initialize(length,width,height)
    @box_length = length
    @box_width = width
    @box_height = height
  end

  def putItem
    puts "盒子的长：#@box_length"
    puts "盒子的宽：#@box_width"
    puts "盒子的高：#@box_height"
  end

  box1 = Box.new(5, 8, 9)
  box1.putItem

end