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模式定义
解释器模式为语言创建解释器,对于特定的计算机程序设计语言,用来解释预先定义的文法。简单地说,解释器模式是一种简单的语法解释器构架。
下图是该模式的类图:
一个生动的例子
Expression接口:
public interface Expression {
boolean interpret(String context);
}
TerminalExpression类:
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;
}
}
Expression实现类:
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);
}
}
Expression实现类:
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);
}
}
测试类/客户端类:
public class InterpreterTest {
public static void main(String[] args) {
Expression robert = new TerminalExpression("Robert");
Expression john = new TerminalExpression("John");
System.out.println(new OrExpression(robert, john).interpret("John"));
System.out.println(new AndExpression(robert, john).interpret("John is Robert"));
}
}
参考
- Head First 设计模式[书籍]
- 菜鸟教程之解释器模式
- 百度百科之解释器模式