四则运算结队学习
代码：
-import java.util.*;
public class fourrule{
public char[] op = {'+','-','*','/','(',')'};
public String[] strOp = {"+","-","*","/","(",")"};
public boolean isDigit(char c){
if(c>='0'&&c<='9'){
return true;
}
return false;
}
public boolean isOp(char c){
for(int i=0;i<op.length;i++){
if(op[i]==c){
return true;
}
}
return false;
}
public boolean isOp(String s){
for(int i=0;i<strOp.length;i++){
if(strOp[i].equals(s)){
return true;
}
}
return false;
}
/**
* 处理输入的计算式
* @param str
* @return
*/
public List<String> work(String str){
List<String> list = new ArrayList<String>();
char c;
StringBuilder sb = new StringBuilder();
for(int i=0;i<str.length();i++){
c = str.charAt(i);
if(isDigit(c)){
sb.append(c);
}
if(isOp(c)){
if(sb.toString().length()>0){
list.add(sb.toString());
sb.delete(0, sb.toString().length());
}
list.add(c+"");
}
}
if(sb.toString().length()>0){
list.add(sb.toString());
sb.delete(0, sb.toString().length());
}
return list;
}
public void printList(List<String> list){
for(String o:list){
System.out.print(o+" ");
}
}
/**
* 中缀表达式转化为后缀表达式
* 1,遇到数字输出
* 2,遇到高优先级的全部出栈
* 3,最后全部出栈
*/
public List<String> InfixToPostfix(List<String> list){
List<String> Postfixlist = new ArrayList<String>();//存放后缀表达式
Stack<String> stack = new Stack<String>();//暂存操作符
//stack.push('#');
for(int i=0;i<list.size();i++){
String s = list.get(i);
if(s.equals("(")){
stack.push(s);
}else if(s.equals("*")||s.equals("/")){
stack.push(s);
}else if(s.equals("+")||s.equals("-")){
if(!stack.empty()){
while(!(stack.peek().equals("("))){
Postfixlist.add(stack.pop());
if(stack.empty()){
break;
}
}
stack.push(s);
}else{
stack.push(s);
}
}else if(s.equals(")")){
while(!(stack.peek().equals("("))){
Postfixlist.add(stack.pop());
}
stack.pop();
}else{
Postfixlist.add(s);
}
if(i==list.size()-1){
while(!stack.empty()){
Postfixlist.add(stack.pop());
}
}
}
return Postfixlist;
}
/**
* 后缀表达式计算
*/
public int doCal(List<String> list){
Stack<Integer> stack = new Stack<Integer>();
for(int i=0;i<list.size();i++){
String s = list.get(i);
int t=0;
if(!isOp(s)){
t = Integer.parseInt(s);
stack.push(t);
}else{
if(s.equals("+")){
int a1 = stack.pop();
int a2 = stack.pop();
int v = a2+a1;
stack.push(v);
}else if(s.equals("-")){
int a1 = stack.pop();
int a2 = stack.pop();
int v = a2-a1;
stack.push(v);
}else if(s.equals("*")){
int a1 = stack.pop();
int a2 = stack.pop();
int v = a2*a1;
stack.push(v);
}else if(s.equals("/")){
int a1 = stack.pop();
int a2 = stack.pop();
int v = a2/a1;
stack.push(v);
}
}
}
return stack.pop();
}
}
import java.util.*;
public class Test {
public static void main(String[] args) {
fourrule lt = new fourrule();
String str = "9+(3-1)*3+10/2";
List<String> list = lt.work(str);
List<String> list2 = lt.InfixToPostfix(list);
System.out.println("原式为："+str);
System.out.print("后缀表达式为：");
lt.printList(list2);
System.out.println(" ");
System.out.println("计算结果为："+lt.doCal(list2));
}
}
缺陷:
代码中无法用Scanner输入，面对不同的计算式需要在Test.java内部修改运算式，由于时间问题，我与我的结对学习伙伴目前只做到了这一步。
运行结果：
结对学习照片：
码云链接：
https://gitee.com/BESTI-IS-JAVA-2018/20165213zqh/tree/master/src