设计模式composite计算器

<pre class="java" name="code"><pre class="java" name="code"><strong><span style="font-size: 13px;">package composite; public class Expression implements Element{ private Element e1,e2; private char op; public Expression(Element e1,Element e2,char op){ this.e1=e1; this.e2=e2; this.op=op; } public double getValue(){ switch(op){ case '+' :return e1.getValue()+e2.getValue(); case '-' :return e1.getValue()-e2.getValue(); case '*' :return e1.getValue()*e2.getValue(); case '/' :return e1.getValue()/e2.getValue(); default: throw new RuntimeException("无效的运算符！"); } } public static void main(String[] args) { Number n1 = new Number(1); Number n2 = new Number(2); Expression e1 = new Expression(n1, n2, '*'); System.out.println(e1.getValue()); } } </span></strong></pre></pre>
package composite;public class Number implements Element{private double num;public Number(double num){this.num=num;}public double getValue(){return num;}}

package composite;interface Element { double getValue();}