Java实现图形界面计算器

第Java实现图形界面计算器}elseif(!str.equals("0.0")){

str=str.substring(0,str.length()-1);//去掉最后一个元素

DisplayBox.setText(str);

privatevoidAddOne(Stringvalue){//增加一个字符

Stringstr;

str=DisplayBox.getText();

if(str.equals("0.0")){//第一次输入

DisplayBox.setText(value);

}else{

str=str+value;

DisplayBox.setText(str);

privateStringretureResult(){//对输入的式子进行运算；基本方法：逆波兰法，中缀转后缀

Stringstring=DisplayBox.getText();

String[]Midfix=breakDown(string);//中缀表达式的数组

String[]suffix=Conversion(Midfix);//得到后缀表达式

Stringresult=Calculation(suffix);//计算后缀表达式结果

returnresult;

privateStringCalculation(String[]suffix){

StackStringstack=newStack();

Stringsymbols="+-*/";//转换为后缀表达式的式子只会有+-*/符号不会有()

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

if(suffix[i]==null){//suffix后面可能出现null故对其筛选不进行下列的操作

continue;

if(symbols.indexOf(suffix[i])=0){//为符号时进行运算

doubletop1;

doubletop2;

doubletop;

switch(suffix[i]){

case"+":

top1=Double.parseDouble(stack.pop());//取栈顶将其转化为double

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

top=top2+top1;

stack.push(String.valueOf(top));//将top转化为String入栈

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"运算过程中除数出现0";

top=top2/top1;

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

break;

}else{//为数字直接入栈

stack.push(suffix[i]);

Stringresult=stack.pop();

returnresult;

privateString[]breakDown(Stringstring){//将(2+3.14)+9分解成(2+3.14)+9便于后续计算

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

StringDigitString="0123456789.";

StringafterSplit="";

for(inti=0;isplit.length;i++){//将2+3.14变成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){//第一个为符号时只在后面加。

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

}else{//为()或=-*/在其两侧加上,

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

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

split=afterSplit.split(",");//产生的字符串数组中只会含+-*/()整数和小数

returnsplit;

privateString[]Conversion(String[]strings){//中缀转后缀

String[]suffix=newString[strings.length];//后缀表达式

intn=0;//suffix的下标

StackStringstack=newStack();

Stringfirst="*/";

Stringsymbols="+-*/()";

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

if(symbols.indexOf(strings[i])=0){//为符号时

if(stack.empty()){

stack.push(strings[i]);

}else{//栈不为空

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

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();//(出栈

}else{//符号为+-

if(first.indexOf(stack.peek())0){//当栈顶不为为*/直接入栈

stack.push(strings[i]);

}else{

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

//栈顶运算符先于当前运算符时,出栈到栈顶运算符低于或栈为空为止

Strings=stack.pop();

suffix[n]=s;

n++;

stack.push(strings[i]);//当前运算符入栈

}else{//为数字直接成为后缀一部分

suffix[n]=strings[i];

n++;

while(!stack.empty()){//清除栈内剩余符号

Strings=stack.pop();

suffix[n]=s;

n++;

returnsuffix;

privatebooleanisTrue(Stringstr){

if(!BracketMatching(str)){//括号匹配

returnfalse;

if(!OperatorIsTrue(str)){//符号格式正确

returnfalse;

returntrue;

privatebooleanOperatorIsTrue(Stringstring){//运算数数量=运算符号数+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){//不是括号不是运算符一定为运算数

NumberOfDigits++;

if(NumberOfDigits!=NumberOfSymblos+1){

returnfalse;

returntrue;

privatebooleanBracketMatching(Stringstring){//判断括号是否匹配，否则报错

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();

}