设计模式-解释器模式

public abstract class Expression{
    // 解析数值,key是参数，value是数字
    public abstract int interpreter(HashMap<String, Integer> var);
}

public class VarExpress extends Expression{
    private String key;
    public VarExpression(String _key){
        this.key = _key;
    }
    // map取
    public int interpreter(HashMap<String, Integer> var){
        return var.get(this.key);
    }
}

public abstract class SymbolExpression extends Expression{
    // 左数值
    protected Expression left;
    // 右数值
    protected Expression right;
    // 初始化
    public SymbolExpression(Expression _left, Expression _right){
        this.left = _left;
        this.right = _right;
    }
}

public class AddExpression extends SymbolExpression{
    public AddExpression(Expression _left, Expression _right){
        super(_left, _right);
    }
    // 进行相加
    public int interpreter(HashMap<String, Integer> var){
        // 取得，两边的变量都保存在HashMap表中，根据left和right变量，进行相加
        return super.left.interpreter(var) + super.right.interpreter(var);
    }
    // 进行相减
    public int interpreter(HashMap<String,Integer> var){
        return super.left.interpreter(var) - super.right.interpreter(var);
    }
}

public class Calculator{
    // 定义表达式
    private Expression expression;
    // 传参
    public Calculator(String expStr){
        // 用于先后顺序
        Stack stack = new Stack();
        // 将表达式拆分
        char[] charArray = expStr.toCharArray();
        // 运算
        Expression left = null;
        Expression right = null;
        for(int i = 0; i < charArray.length; i++){
            switch(charArray[i]){
                case '+'
                    // 出栈
                    left = stack.pop();
                    right = new VarExpression(String.valueOf(chrArray[++i]));
                    // 将结果入栈
                    stack.push(new AddExpression(left, right));
                    break;
                 case '-'
                     // 放入栈中
                     left = stack.pop();
                     right = new VarExpression(String.valueOf(charArray[++i]));
                     stack.push(new SubExpression(left,right));
                     break;
                  default:
                      stack.push(new VarExpression(String.value(charArray[i])));
            }
        }
        // 运算结果抛出
        this.expression = stack.pop();
    }
    // 运算
    public int run(HashMap<String, Integer> var){
        return this.expression.interpreter(var);
    }
}

public class Client{
    public static void main(String[] args) throws IOException{
        String expStr = getExpStr();
        // 赋值
        HashMap<String, Integer> var = getValue(expStr);
        Calculator cal = new Calculator(expStr);
        System.out.println("运算");
    }
    // 获得表达式
    public static String getExpStr() throws IOException{
        // 新建一个缓冲区，从缓冲区中读取数据
        return (new BufferedReader(new InputStreamReader(System.in))).readLine();
    }
    // 获得值映射
    public static HashMap<String, Integer> getValue(String expStr) throws IOException{
        HashMap<String, Integer> map = new HashMap<String, Integer>();
        // 解析
        for(char ch:exprStr.toCharArray()){
            if(ch != '+' && != '-'){
                if(!map.containsKey(String.valueOf(ch))){
                    // 从缓冲区中，读取整行
                    String in = (new BufferReader(new InputStreamReader(System.in))).readLine();
                }
            }
        }
        return map;
    }
}