If I wrote it complains

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Package stack; 

/* * 
* Created with IntelliJ IDEA. 
* 
* @ author: heiye 
* @ Date: 2020/3/23 
* @ Time: 
 then* Description: No Description 
*/
Public class OperationStackDemo {
Public static void main (String [] args) {
//infix expression 
String expression="3 * 7 + 1 to 25 + 4/2"; 
//define the number and symbol stack 
OperStack numStack=new OperStack (10); 
OperStack OperStack=new OperStack (10); 

//define variables operation need 
int index=0; 
char ch; 
Int res; 
String keepNum=""; 
While (true) {
//traversal access to every single character in the string 
Ch=expression. The substring (index, + + index). The charAt (0); 
//it is take the character of digital or operator 
{if (operStack. IsOper (ch)) 
//if the operator, you will need to determine whether the current symbol stack exists operator 
if (! OperStack. IsEmpty ()) {
//if there is need to determine whether the current operator operator then smaller than that in the stack operator 
Int oper=operStack. Peek (); 
If (operStack. OperFlag (ch) & lt;=operStack. OperFlag (oper)) {
//if less than you need to pop up the stack operations operator 
Operation (operStack numStack); 
//the stack will be added to the current operator symbol 
OperStack. Push (ch); 
} else {
//if the is equal to or greater than the direct deposit can 
OperStack. Push (ch); 
} 
} else {
//if the null is directly inserted into the 
OperStack. Push (ch); 
} 
} else {
//if the digital direct deposit to the number of stack 
//implementation a number of digital computing 
KeepNum +=ch; 
If (index & gt;=expression. The length ()) {
NumStack. Push (Integer. ParseInt (keepNum)); 
} else {
If (operStack. IsOper (expression. CharAt (index))) {
NumStack. Push (Integer. ParseInt (keepNum)); 
KeepNum=""; 
} 
} 
} 

//determine whether intercept out 
If (index & gt;=expression. The length ()) {
break; 
} 
} 

//pop-up number and symbol stack respectively calculated 
While (true) {
//if the stack is empty, the number of the stack is the result of final number 
if (! OperStack. IsEmpty ()) {
//calculate 
Operation (operStack numStack); 
} else {
//is empty is getting the results 
Res=numStack. Prop (); 
break; 
} 
} 

System. The out. Println (" the final computation results: "+ res); 
} 

Public static void operation (OperStack OperStack, OperStack numStack) {
Int oper=operStack. Prop (); 
Int num1=numStack. Prop (); 
Int num2=numStack. Prop (); 

//will result in the stack in the 
Int res=operStack. Operation (num1, num2, oper); 
NumStack. Push (res); 
} 
} 

The class OperStack {
Private int maxSize; 
Private int [] stack; 
Private int top; 

Public OperStack (int maxSize) {
this.maxSize=maxSize; 
Stack=new int [this maxSize]; 
Top=1; 
} 

/* * 
* determine whether stack empty 
* 
* @ return 
*/
Public Boolean isEmpty () {
Return the top==1; 
} 

/* * 
* stack full 
* 
* @ return 
*/
Public Boolean isFull () {
Return the top==this. MaxSize - 1; 
} 

/* * 
* data is added to the stack 
* 
* @ param data 
*/
Public void push (int data) {
//determine whether full before you add 
If (isFull ()) {
System. Out.println (" stack is full!" ); 
return; 
} 
Top++; 
Stack [top]=data; 
} 

/* * 
* flare stack 
* 
* @ return 
*/
Public int prop () {
//determine whether empty before you play 
If (isEmpty ()) {
System. Out.println (" stack is empty!" ); 
return 0; 
} 
The int value=https://bbs.csdn.net/topics/stack [top]; 
Top -; 
return value; 
} 

/* * 
* view the stack 
*/
Public void show () {
If (isEmpty ()) {
System. Out.println (" stack is empty!" ); 
return; 
} 
Int I=top; 
While (I & gt; 1) {
System. The out. Println (" stack data: "+ stack [I]); 
I -; 
} 
} 

/* * 
* determine whether symbol 
* 
* @ param ch 
*/
Public Boolean isOper (char ch) {
Return ch=='*' | | ch=='/' | | ch=='+' | | ch=='-'; 
} 

/* * 

 * arithmetic method* 
* @ param num1 
* @ param num2 
* @ param oper 
* @ return 
*/
Public int operation (int num1, int num2, int oper) {
int res=0; 
The switch (oper) {
Case: '*' 
Res=num1 * num2; 
break; 
Case '/' : 
Res=num2/num1; 
break; 
Case: '+' 
Res=num1 + num2; 
break; 
In case the '-' : 
Res=num2 - num1; 
break; 
Default: 
System. The out. Println (" temporarily does not support the operator ~ "); 
break; 
} 
return res; 
} 

/* * 
* judgment symbol priority 
* 
* @ param ch 
* @ return 
*/
Public int operFlag int (ch) {
Char [] chars={' + ', '-' and '*', '/'}; 
Int ZERO equals ZERO, ONE,=1, TWO=2, THREE=3; 
If (ch==chars [TWO] | | ch==chars [THREE]) {
return 1; 
} else if (ch==chars (ZERO) | | ch==chars [ONE]) {
return 0; 
} else {
return -1; 
} 
} 

/* * 
* access to the first element on the top of the stack 
* 
* @ return 
*/
Public int peek () {
The return stack [top]; 
} 
} 

Just before you have written a infix expression calculator small case

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The string to replace the keyboard