无涯教程将创建一个 Expression 接口和实现 Expression 接口的具体类。定义了一个 TerminalExpression 类,该类充当所讨论上下文的主要解释器。其他类 OrExpression , AndExpression 用于创建组合表达式。
演示类 InterpreterPatternDemo 将使用 Expression 类创建规则并演示表达式的解析。
第1步 - 创建一个表达式接口。
Expression.java
public interface Expression { public boolean interpret(String context); }
第2步 - 创建实现上述接口的具体类。
TerminalExpression.java
public 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; } }
OrExpression.java
public 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); } }
AndExpression.java
public 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); } }
第3步 - InterpreterPatternDemo 使用 Expression 类创建规则,然后解析它们。
InterpreterPatternDemo.java
public class InterpreterPatternDemo { //Rule: Robert and John are male public static Expression getMaleExpression(){ Expression robert = new TerminalExpression("Robert"); Expression john = new TerminalExpression("John"); return new OrExpression(robert, john); } //Rule: Julie is a married women 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")); } }
第4步 - 验证输出。
John is male? true Julie is a married women? true
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PPT设计进阶 · 从基础操作到高级创意 -〔李金宝(Bobbie)〕