java语言实现中缀表达式转换为后缀表达式

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Stack;
import java.util.regex.Pattern;

import org.springframework.util.StringUtils;

/**
 * @ClassName:     PostfixExpression.java
 * @Description:   中缀变后缀表达式
 * @author:        ma-zhuo
 * @version:       V1.0  
 * @Date:          2019年11月25日 下午3:37:53 
 */
public class PostfixExpression {

	private static String[] one = {"+","-"};
	private static String[] two = {"*","/"};
	private static ArrayList<Object> InfixList = new ArrayList<Object>();  //中缀表达式
	private static Stack<String> opStack = new Stack<String>();
	private static ArrayList<Object> suffixList = new ArrayList<Object>();  //后缀表达式
	
	/**
	 * @Description: 该方法实现将字符串中的每个数字和符号转化放进InfixList列表中
	 * @param @param expression 中缀字符串
	 * @throws
	 */
	private static void InffixList(String expression){
		StringBuilder sb = new StringBuilder();
		for (int i = 0; i<expression.length(); i++) {
			String a = expression.substring(i,i+1);
			if(a.equals(".")){
				sb.append(a);
			}else if(isNum(a)){
				sb.append(a);
			}else{
				if(sb.length() != 0){
					InfixList.add(sb.toString());
					sb = new StringBuilder();
				}
				InfixList.add(a);
			}
			if(i == (expression.length() - 1)){
				InfixList.add(sb.toString());
			}
		}
	}
	
	/**
	 * @Title: isNum 
	 * @Description: 判断str是否是数字（只匹配正数,小数或者正数都可以）
	 * @return boolean    返回类型 
	 * @throws
	 */
	private static boolean isNum(String str){
		if(StringUtils.isEmpty(str)){
			return false;
		}
		Pattern pattern = Pattern.compile("^(0|[1-9][0-9]*)(\\.\\d+)?$");
		return pattern.matcher(str).matches();
	}
	
	/**
	 * @Title: priority 
	 * @Description: 判断两个运算符的优先级
	 * @return boolean a高于b,返回true；反之返回false 
	 * @throws
	 */
	private static boolean priority(String a,String b){
		if(StringUtils.isEmpty(a) || StringUtils.isEmpty(b)){
			return false;
		}
		int aa = 0,bb = 0;
		if(Arrays.asList(one).contains(a)){
			aa = 1;
		}else if(Arrays.asList(two).contains(a)){
			aa = 2;
		}else if(a.equals("(")){
			aa = 0;
		}
		if(Arrays.asList(one).contains(b)){
			bb = 1;
		}else if(Arrays.asList(two).contains(b)){
			bb = 2;
		}else if(b.equals("(")){
			bb = 0;
		}
		return (aa-bb) > 0;
	}
	
	//开始转换后缀表达式
	public static String getSuffixList(String expression){
		InffixList(expression);
		System.out.println("从字符串中提取出元素："+InfixList.toString());
		
		for (Object object : InfixList) {
			if(isNum(object.toString())){
				suffixList.add(object);
			}else{
				//判断栈是否为空，如果为空则直接放入
				if(opStack.empty()){
					opStack.push(object.toString());
				}else if(object.toString().equals("(")){
					opStack.push(object.toString());
				}else if(object.toString().equals(")")){
					while(!opStack.peek().equals("(")){
						String a = opStack.pop();
						suffixList.add(a);
					}
					opStack.pop();
				}else{
					//如果不为空,则取出比较
					while(true){
						if(opStack.empty()){
							opStack.push(object.toString());
							break;
						}else if(priority(object.toString(), opStack.peek())){
							opStack.push(object.toString());
							break;
						}else{
							String a = opStack.pop();
							suffixList.add(a);
						}
					}
				}
			}
		}
		while(!opStack.empty()){
			suffixList.add(opStack.pop());
		}
		return suffixList.toString();
	}
}

import com.example.stack.postfixExpression.PostfixExpression;

/**
 * @ClassName:     TestStack.java
 * @Description:   TODO
 * @author:        mazhuo
 * @version:       V1.0  
 * @Date:          2019年11月26日 上午9:18:09 
 */
public class TestStack {

	/** 
	 * @Title: main 
	 * @Description: TODO
	 * @param @param args    设定文件 
	 * @return void    返回类型 
	 * @throws 
	 */
	public static void main(String[] args) {

		String str = "10.23+2*3+(4*5+6)*7";
		String suffix = PostfixExpression.getSuffixList(str);
		System.out.println("后缀表达式："+suffix);
	}

}

输出结果