海南 网站 建设,土巴兔装修,网络营销推广难做吗,友情链接系统使用递归和解释器模式 程序结构设计具体实现1. 先上最重要的实现类#xff1a;ExpressionParser#xff08;最重要#xff09;2. 再上上下文测试代码#xff1a;Context#xff08;程序入口#xff0c;稍重要#xff09;3. 使用到的接口和数据结构#xff08;不太重要的… 使用递归和解释器模式 程序结构设计具体实现1. 先上最重要的实现类ExpressionParser最重要2. 再上上下文测试代码Context程序入口稍重要3. 使用到的接口和数据结构不太重要的结构封装3.1 interface3.1.1 NumberExpression3.1.2 四则运算Expression实现类3.1.2.1 AddExpression3.1.2.2 SubtractExpression3.1.2.3 MultiplyExpression3.1.2.4 DivideExpression 程序结构设计
Context 编写测试代码 expression Expression interface 四则运算Expression implement NumberExpression implement ExpressionParser 核心实现类
具体实现
1. 先上最重要的实现类ExpressionParser最重要
package com.example.demo;import com.example.demo.expression.*;import java.util.regex.Matcher;
import java.util.regex.Pattern;public class ExpressionParser {private String input;private int index;public ExpressionParser(String input) {this.input input.replaceAll(\\s, ); // 移除空格this.index 0;}public Expression parse() {return parseExpression();}private Expression parseExpression() {Expression left parseTerm();while (index input.length()) {char operator input.charAt(index);if (operator || operator -) {index;Expression right parseTerm();if (operator ) {left new AddExpression(left, right);} else {left new SubtractExpression(left, right);}} else {break;}}return left;}private Expression parseTerm() {Expression left parseFactor();while (index input.length()) {char operator input.charAt(index);if (operator * || operator /) {index;Expression right parseFactor();if (operator *) {left new MultiplyExpression(left, right);} else {left new DivideExpression(left, right);}} else {break;}}return left;}private Expression parseFactor() {if (index input.length()) {char currentChar input.charAt(index);if (Character.isDigit(currentChar)) {return parseNumber();} else if (currentChar () {index;Expression expression parseExpression();if (index input.length() input.charAt(index) )) {index;return expression;} else {throw new IllegalArgumentException(Mismatched parentheses);}}}throw new IllegalArgumentException(Invalid expression);}private Expression parseNumber() {Pattern numberPattern Pattern.compile(\\d);Matcher matcher numberPattern.matcher(input.substring(index));if (matcher.find()) {String numberStr matcher.group();index numberStr.length();return new NumberExpression(Integer.parseInt(numberStr));} else {throw new IllegalArgumentException(Invalid number);}}
}
2. 再上上下文测试代码Context程序入口稍重要
package com.example.demo;import com.example.demo.expression.Expression;public class Context {public static void main(String[] args) {String inputExpression (3 55) * 2 - 4 / 2;ExpressionParser parser new ExpressionParser(inputExpression);Expression expression parser.parse();int result expression.interpret();System.out.println(Result: result);}
}
3. 使用到的接口和数据结构不太重要的结构封装
3.1 interface
package com.example.demo.expression;public interface Expression {int interpret();
}3.1.1 NumberExpression
package com.example.demo;import com.example.demo.expression.Expression;public class NumberExpression implements Expression {private int number;public NumberExpression(int number) {this.number number;}Overridepublic int interpret() {return number;}
}3.1.2 四则运算Expression实现类
3.1.2.1 AddExpression
package com.example.demo.expression;public class AddExpression implements Expression {private Expression left;private Expression right;public AddExpression(Expression left, Expression right) {this.left left;this.right right;}Overridepublic int interpret() {return left.interpret() right.interpret();}
}3.1.2.2 SubtractExpression
package com.example.demo.expression;// 非终结符表达式减法表达式
public class SubtractExpression implements Expression {private Expression left;private Expression right;public SubtractExpression(Expression left, Expression right) {this.left left;this.right right;}Overridepublic int interpret() {return left.interpret() - right.interpret();}
}3.1.2.3 MultiplyExpression
package com.example.demo.expression;// 非终结符表达式乘法表达式
public class MultiplyExpression implements Expression {private Expression left;private Expression right;public MultiplyExpression(Expression left, Expression right) {this.left left;this.right right;}Overridepublic int interpret() {return left.interpret() * right.interpret();}
}3.1.2.4 DivideExpression
package com.example.demo.expression;// 非终结符表达式除法表达式
public class DivideExpression implements Expression {private Expression left;private Expression right;public DivideExpression(Expression left, Expression right) {this.left left;this.right right;}Overridepublic int interpret() {int divisor right.interpret();if (divisor ! 0) {return left.interpret() / divisor;} else {throw new ArithmeticException(Division by zero);}}
}
