第Java實現圖形界面計算器}elseif(!str.equals("0.0")){

str=str.substring(0,str.length()-1);//去掉最后一個元素

DisplayBox.setText(str);

privatevoidAddOne(Stringvalue){//增加一個字符

Stringstr;

str=DisplayBox.getText();

if(str.equals("0.0")){//第一次輸入

DisplayBox.setText(value);

}else{

str=str+value;

DisplayBox.setText(str);

privateStringretureResult(){//對輸入的式子進行運算；基本方法：逆波蘭法，中綴轉后綴

Stringstring=DisplayBox.getText();

String[]Midfix=breakDown(string);//中綴表達式的數組

String[]suffix=Conversion(Midfix);//得到后綴表達式

Stringresult=Calculation(suffix);//計算后綴表達式結果

returnresult;

privateStringCalculation(String[]suffix){

StackStringstack=newStack();

Stringsymbols="+-*/";//轉換為后綴表達式的式子只會有+-*/符號不會有()

for(inti=0;isuffix.length;i++){

if(suffix[i]==null){//suffix后面可能出現null故對其篩選不進行下列的操作

continue;

if(symbols.indexOf(suffix[i])=0){//為符號時進行運算

doubletop1;

doubletop2;

doubletop;

switch(suffix[i]){

case"+":

top1=Double.parseDouble(stack.pop());//取棧頂將其轉化為double

top2=Double.parseDouble(stack.pop());

top=top2+top1;

stack.push(String.valueOf(top));//將top轉化為String入棧

break;

case"-":

top1=Double.parseDouble(stack.pop());

top2=Double.parseDouble(stack.pop());

top=top2-top1;

stack.push(String.valueOf(top));

break;

case"*":

top1=Double.parseDouble(stack.pop());

top2=Double.parseDouble(stack.pop());

top=top2*top1;

stack.push(String.valueOf(top));

break;

case"/":

top1=Double.parseDouble(stack.pop());

top2=Double.parseDouble(stack.pop());

if(top1==0){

return"運算過程中除數出現0";

top=top2/top1;

stack.push(String.valueOf(top));

break;

}else{//為數字直接入棧

stack.push(suffix[i]);

Stringresult=stack.pop();

returnresult;

privateString[]breakDown(Stringstring){//將(2+3.14)+9分解成(2+3.14)+9便于后續計算

String[]split=string.split("");

StringDigitString="0123456789.";

StringafterSplit="";

for(inti=0;isplit.length;i++){//將2+3.14變成2,+,3.14便于拆分

if(DigitString.indexOf(split[i])=0){

afterSplit=afterSplit+split[i];

}elseif(afterSplit.equals("")DigitString.indexOf(split[i])0){//第一個為符號時只在后面加。

afterSplit=afterSplit+split[i]+",";

}else{//為()或=-*/在其兩側加上,

afterSplit=afterSplit+","+split[i]+",";

afterSplit=afterSplit.replace(",,",",");//避免(2+3)+2產生……3,),,+,2

split=afterSplit.split(",");//產生的字符串數組中只會含+-*/()整數和小數

returnsplit;

privateString[]Conversion(String[]strings){//中綴轉后綴

String[]suffix=newString[strings.length];//后綴表達式

intn=0;//suffix的下標

StackStringstack=newStack();

Stringfirst="*/";

Stringsymbols="+-*/()";

for(inti=0;istrings.length;i++){

if(symbols.indexOf(strings[i])=0){//為符號時

if(stack.empty()){

stack.push(strings[i]);

}else{//棧不為空

if(first.indexOf(strings[i])=0||strings[i].equals("(")){//為+/(直接入棧

stack.push(strings[i]);

}elseif(strings[i].equals(")")){

Stringtop=stack.peek();

while(!top.equals("(")){

top=stack.pop();

suffix[n]=top;

n++;

top=stack.peek();

stack.pop();//(出棧

}else{//符號為+-

if(first.indexOf(stack.peek())0){//當棧頂不為為*/直接入棧

stack.push(strings[i]);

}else{

while(!stack.empty()first.indexOf(stack.peek())=0)

//棧頂運算符先于當前運算符時,出棧到棧頂運算符低于或棧為空為止

Strings=stack.pop();

suffix[n]=s;

n++;

stack.push(strings[i]);//當前運算符入棧

}else{//為數字直接成為后綴一部分

suffix[n]=strings[i];

n++;

while(!stack.empty()){//清除棧內剩余符號

Strings=stack.pop();

suffix[n]=s;

n++;

returnsuffix;

privatebooleanisTrue(Stringstr){

if(!BracketMatching(str)){//括號匹配

returnfalse;

if(!OperatorIsTrue(str)){//符號格式正確

returnfalse;

returntrue;

privatebooleanOperatorIsTrue(Stringstring){//運算數數量=運算符號數+1

String[]split=breakDown(string);

Stringsymblos="+-*/";

Stringbracket="()";

intNumberOfDigits=0;

intNumberOfSymblos=0;

for(inti=0;isplit.length;i++){

if(symblos.indexOf(split[i])=0){

NumberOfSymblos++;

}elseif(bracket.indexOf(split[i])0){//不是括號不是運算符一定為運算數

NumberOfDigits++;

if(NumberOfDigits!=NumberOfSymblos+1){

returnfalse;

returntrue;

privatebooleanBracketMatching(Stringstring){//判斷括號是否匹配，否則報錯

char[]split=string.toCharArray();

StackCharacterstack=newStack();

for(inti=0;isplit.length;i++){

if(split[i]=='('){

stack.push(split[i]);

}elseif(!stack.empty()split[i]==')'){

stack.pop();

}