java.util.stack 适合带有小括号的算术运算
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java.util.stack，继承自Vector
FILO, 适合带有小括号的算术运算
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import java.util.Stack;
/**?
?* 利用栈，进行四则运算的类?
?* 用两个栈来实现算符优先，一个栈用来保存需要计算的数据numStack,一个用来保存计算优先符priStack?
?*?
?* 基本算法实现思路为：用当前取得的运算符与priStack栈顶运算符比较优先级：若高于，则因为会先运算，放入栈顶；?
?* 若等于，因为出现在后面，所以会后计算，所以栈顶元素出栈，取出操作数运算；?
?* 若小于，则同理，取出栈顶元素运算，将结果入操作数栈。各个优先级'(' > '*' = '/' > '+' = '-' > ')'?
?*?
?*/
public class Operate {??
??private Stack<Character> priStack = new Stack<Character>();// 操作符栈??
??private Stack<Integer> numStack = new Stack<Integer>();;// 操作数栈??
???
??/**?
???* 传入需要解析的字符串，返回计算结果(此处因为时间问题，省略合法性验证)?
???* @param str 需要进行技术的表达式?
???* @return 计算结果?
???*/
??public int caculate(String str) {??
????// 1.判断string当中有没有非法字符??
????String temp;// 用来临时存放读取的字符??
????// 2.循环开始解析字符串，当字符串解析完，且符号栈为空时，则计算完成??
????StringBuffer tempNum = new StringBuffer();// 用来临时存放数字字符串(当为多位数时)??
????StringBuffer string = new StringBuffer().append(str);// 用来保存，提高效率??
???
????while (string.length() != 0) {??
??????temp = string.substring(0, 1);??
??????string.delete(0, 1);??
??????// 判断temp，当temp为操作符时??
??????if (!isNum(temp)) {??
????????// 1.此时的tempNum内即为需要操作的数，取出数，压栈，并且清空tempNum??
????????if (!"".equals(tempNum.toString())) {??
??????????// 当表达式的第一个符号为括号??
??????????int num = Integer.parseInt(tempNum.toString());??
??????????numStack.push(num);
??????????tempNum.delete(0, tempNum.length());??
????????}??
????????// 用当前取得的运算符与栈顶运算符比较优先级：若高于，则因为会先运算，放入栈顶；若等于，因为出现在后面，所以会后计算，所以栈顶元素出栈，取出操作数运算；??
????????// 若小于，则同理，取出栈顶元素运算，将结果入操作数栈。??
???
????????// 判断当前运算符与栈顶元素优先级，取出元素，进行计算(因为优先级可能小于栈顶元素，还小于第二个元素等等，需要用循环判断)??
????????while (!compare(temp.charAt(0)) && (!priStack.empty())) {?
??????????int a = (int) numStack.pop();// 第二个运算数??
??????????int b = (int) numStack.pop();// 第一个运算数??
??????????char ope = priStack.pop();??
??????????int result = 0;// 运算结果??
??????????switch (ope) {??
??????????// 如果是加号或者减号，则??
??????????case '+':??
????????????result = b + a;??
????????????// 将操作结果放入操作数栈??
????????????numStack.push(result);??
????????????break;??
??????????case '-':??
????????????result = b - a;??
????????????// 将操作结果放入操作数栈??
????????????numStack.push(result);??
????????????break;??
??????????case '*':??
????????????result = b * a;??
????????????// 将操作结果放入操作数栈??
????????????numStack.push(result);??
????????????break;??
??????????case '/':??
????????????result = b / a;// 将操作结果放入操作数栈??
????????????numStack.push(result);??
????????????break;??
??????????}??
???
????????}??
????????// 判断当前运算符与栈顶元素优先级， 如果高，或者低于平，计算完后，将当前操作符号，放入操作符栈??
????????if (temp.charAt(0) != '#') {??
??????????priStack.push(new Character(temp.charAt(0)));??
??????????if (temp.charAt(0) == ')') {// 当栈顶为'('，而当前元素为')'时，则是括号内以算完，去掉括号??
????????????priStack.pop();??
????????????priStack.pop();??
??????????}??
????????}??
??????} else
????????// 当为非操作符时（数字）??
????????tempNum = tempNum.append(temp);// 将读到的这一位数接到以读出的数后(当不是个位数的时候)??
????}??
????return numStack.pop();??
??}??
???
??/**?
???* 判断传入的字符是不是0-9的数字?
???*?
???* @param str?
???*????? 传入的字符串?
???* @return?
???*/
??private boolean isNum(String temp) {??
????return temp.matches("[0-9]");??
??}??
???
??/**?
???* 比较当前操作符与栈顶元素操作符优先级，如果比栈顶元素优先级高，则返回true，否则返回false?
???*?
???* @param str 需要进行比较的字符?
???* @return 比较结果 true代表比栈顶元素优先级高，false代表比栈顶元素优先级低?
???*/
??private boolean compare(char str) {??
????if (priStack.empty()) {??
??????// 当为空时，显然 当前优先级最低，返回高??
??????return true;??
????}??
????char last = (char) priStack.lastElement();??
????// 如果栈顶为'('显然，优先级最低，')'不可能为栈顶。??
????if (last == '(') {??
??????return true;??
????}??
????switch (str) {??
????case '#':??
??????return false;// 结束符??
????case '(':??
??????// '('优先级最高,显然返回true??
??????return true;??
????case ')':??
??????// ')'优先级最低，??
??????return false;??
????case '*': {??
??????// '*/'优先级只比'+-'高??
??????if (last == '+' || last == '-')??
????????return true;??
??????else
????????return false;??
????}??
????case '/': {??
??????if (last == '+' || last == '-')??
????????return true;??
??????else
????????return false;??
????}??
??????// '+-'为最低，一直返回false??
????case '+':??
??????return false;??
????case '-':??
??????return false;??
????}??
????return true;??
??}??
???
??public static void main(String args[]) {??
????Operate operate = new Operate();??
????int t = operate.caculate("(3+4*(4*10-10/2)#");???
????System.out.println(t);??
??}??
???
}
|
补充：java stack实现的中缀简单四则运算表达式计算
我就废话不多说了，大家还是直接看代码吧~
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public abstract class Stack<T> {
??public abstract boolean isEmpty();
??public abstract boolean isFull();
??public abstract T top();
??public abstract boolean push(T x);
??public abstract T pop();
??public abstract void clear();
}
|
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public class SeqStack<T> extends Stack<T> {
??private Object[] elementData;
??private int maxTop;
??private int top;
??public SeqStack(int size) {
????this.maxTop = size - 1;
????elementData = new Object[size];
????top = -1;
??}
??@Override
??public boolean isEmpty() {
????return top == -1;
??}
??@Override
??public boolean isFull() {
????return top == maxTop - 1;
??}
??@SuppressWarnings("unchecked")
??@Override
??public T top() {
????if (top == -1) {
??????System.out.println("Empty");
??????return null;
????}
????return (T) elementData[top];
??}
??@Override
??public boolean push(T x) {
????if (top == maxTop) {
??????System.err.println("Full");
??????return false;
????}
????elementData[++top] = x;
????return true;
??}
??@SuppressWarnings("unchecked")
??@Override
??public T pop() {
????if (top == -1) {
??????System.err.println("Empty");
??????return null;
????}
????
????T result = (T)elementData[top];
????elementData[top] = null; //gc
????top--;
????return result;
??}
??@Override
??public void clear() {
????
????//let gc do its work
????for(int i = 0; i < top+1; i++) {
??????
??????elementData[i] = null;
????}
????
????top = -1;
??}
}
|
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public class StackCalc {
??private SeqStack<Integer> stack;
??public StackCalc(int maxSize) {
????stack = new SeqStack<Integer>(maxSize);
??}
??private void pushOperand(Integer number) {
????stack.push(number);
??}
??private Number doOperate(char oper) {
????Integer right = stack.pop();
????Integer left = stack.pop();
????Integer result = null;
????if (left != null && right != null) {
??????switch (oper) {
??????case '+':
????????result = left.intValue() + right.intValue();
????????break;
??????case '-':
????????result = left.intValue() - right.intValue();
????????break;
??????case '*':
????????result = left.intValue() * right.intValue();
????????break;
??????case '/':
????????if (right.intValue() == 0) {
??????????System.err.println("Divide by 0");
????????}
????????result = left.intValue() / right.intValue();
????????break;
??????default:
????????break;
??????}
????}
????stack.push(result);
????return result;
??}
??private int icp(char c) {
????switch (c) {
????case '#':
??????return 0;
????case '(':
??????return 7;
????case '*':
??????return 4;
????case '/':
??????return 4;
????case '+':
??????return 2;
????case '-':
??????return 2;
????case ')':
??????return 1;
????default:
??????return -1;
????}
??}
??private int isp(int c) {
????switch (c) {
????case '#':
??????return 0;
????case '(':
??????return 1;
????case '*':
??????return 5;
????case '/':
??????return 5;
????case '+':
??????return 3;
????case '-':
??????return 3;
????case ')':
??????return 7;
????default:
??????return -1;
????}
??}
??public String transfer(String expression) {
????StringBuilder sb = new StringBuilder();
????SeqStack<Character> stack = new SeqStack<Character>(expression.length());
????stack.push('#');
????for (int i = 0; i < expression.length(); i++) {
??????Character c = expression.charAt(i);
??????if ('0' <= c && c <= '9' || 'a' <= c && c <= 'z' ||
??????????'A' <= c && c <= 'Z') { // digit character
????????sb.append(c);
??????} else { // 操作符
????????if (icp(c) > isp(stack.top())) { // 进栈
??????????stack.push(c);
????????} else { // 出栈
??????????if (c == ')') {
????????????char ch = stack.pop();
????????????while (ch != '(') {
??????????????sb.append(ch);
??????????????ch = stack.pop();
????????????}
??????????} else {
????????????char ch = stack.pop();
????????????while (icp(c) <= isp(ch)) {
??????????????sb.append(ch);
??????????????ch = stack.pop();
????????????}
????????????stack.push(ch);
????????????stack.push(c);
??????????}
????????}
??????}
????} // end of for
????char ch = stack.pop();
????while (ch != '#') {
??????
??????sb.append(ch);
??????ch = stack.pop();
????}
????stack.clear();???
????return sb.toString();
??}
??public Integer calc(String expression) {
????expression = transfer(expression);
????for (int i = 0; i < expression.length(); i++) {
??????char c = expression.charAt(i);
??????switch (c) {
??????case '+':
??????case '-':
??????case '*':
??????case '/':
????????doOperate(c);
????????break;
??????default:
????????pushOperand(new Integer(c + ""));
????????break;
??????}
????}
????return stack.pop();
??}
??/**
???* @param args
???*/
??public static void main(String[] args) {
????StackCalc calc = new StackCalc(10);
????System.out.println(calc.calc("6/(4-2)+3*2"));
??}
}
|
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