303解释器模式

定义

解释器模式（Interpreter Pattern）提供了评估语言的语法或表达式的方式，它属于行为型模式。这种模式实现了一个表达式接口，该接口解释一个特定的上下文。这种模式被用在 SQL 解析、符号处理引擎等。

类图

代码

public class InterpreterPattern {
    //规则：Robert 和 John 是男性
    public static Expression getMaleExpression(){
        Expression robert = new TerminalExpression("Robert");
        Expression john = new TerminalExpression("John");
        return new OrExpression(robert, john);
    }

    //规则：Julie 是一个已婚的女性
    public static Expression getMarriedWomanExpression(){
        Expression julie = new TerminalExpression("Julie");
        Expression married = new TerminalExpression("Married");
        return new AndExpression(julie, married);
    }
    public static void main(String[] args) {
        Expression isMale = getMaleExpression();
        Expression isMarriedWoman = getMarriedWomanExpression();

        System.out.println("John is male? " + isMale.interpret("John"));
        System.out.println("Julie is a married women? "
                + isMarriedWoman.interpret("Married Julie"));

    }
}

interface Expression {
    public boolean interpret(String context);
}
class TerminalExpression implements Expression {
    private String data;
    public TerminalExpression(String data){
        this.data = data;
    }
    @Override
    public boolean interpret(String context) {
        if(context.contains(data)){
            return true;
        }
        return false;
    }
}
class OrExpression implements Expression {
    private Expression expr1 = null;
    private Expression expr2 = null;
    public OrExpression(Expression expr1, Expression expr2) {
        this.expr1 = expr1;
        this.expr2 = expr2;
    }
    @Override
    public boolean interpret(String context) {
        return expr1.interpret(context) || expr2.interpret(context);
    }
}
class AndExpression implements Expression {
    private Expression expr1 = null;
    private Expression expr2 = null;
    public AndExpression(Expression expr1, Expression expr2) {
        this.expr1 = expr1;
        this.expr2 = expr2;
    }
    @Override
    public boolean interpret(String context) {
        return expr1.interpret(context) && expr2.interpret(context);
    }
}