什么是中序表达式
前序(前缀)表达式要求每一个操作符出现在其操作数之前.一般不用. 写表达式的后序表达式一般是为了便利于计算机编程中栈的实现,所以用的较多.
具体代码如下所示：
package 表达式求值;
import java.util.Stack;
/*
* 中序表达式求值实现
*/
public class CenterExpression {
public double evaluate(String expression){ //传入中序表达式
char [] ex = expression.toCharArray();
Stack<Double> num = new Stack<>();
Stack<Character> ops = new Stack<>();
for(int i = 0; i < ex.length; i++){ //循环将表达式依次入栈
char c = ex[i];
if(c < '9' && c > '0'){
num.push(Double.parseDouble(Character.toString(c)));
}
else if(c == '('){
ops.push('(');
}
else if(c == ')'){
while(true){
char op = ops.pop();
if(op == '('){
break;
}
else{
switch(op){
case '+':num.push(num.pop()+num.pop());break;
case '-':num.push(num.pop()-num.pop());break;
case '*':num.push(num.pop()*num.pop());break;
case '/':num.push(num.pop()/num.pop());break;
default:break;
}
}
}
}
else if(ops.empty() && (c == '+' || c == '-' || c == '*' || c == '/')){
ops.push(c);
}
else if(!ops.isEmpty() && (c == '+' || c == '-' || c == '*' || c == '/')){
char op =ops.peek();
while((op == '*' || op == '/') && (c == '+' || c == '-')){
op = ops.pop();
switch(op){
case '+':num.push(num.pop()+num.pop());break;
case '-':num.push(num.pop()-num.pop());break;
case '*':num.push(num.pop()*num.pop());break;
case '/':num.push(num.pop()/num.pop());break;
default:break;
}
if(ops.isEmpty()){
break;
}
else{
op = ops.peek();
}
}
ops.push(c);
}
}
while(!ops.isEmpty()){ //处理剩余可以按计算机扫描顺序处理的表达式
char op =ops.pop();
switch(op){
case '+':num.push(num.pop()+num.pop());break;
case '-':num.push(num.pop()-num.pop());break;
case '*':num.push(num.pop()*num.pop());break;
case '/':num.push(num.pop()/num.pop());break;
default:break;
}
}
return num.pop();
}
public static void main(String [] args){
CenterExpression exp = new CenterExpression();
System.out.println(exp.evaluate("1*2+5*3"));
}
}
以上所述是小编给大家介绍的Java实现中序表达式的实例代码，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对脚本之家网站的支持！
