算符优先法 设计一个带（）的计算器

Question

这个问题 可能比较棘手！能计算一个： 7+(8+2*2)/3-1=10;就好了 

Answer 1

antlr 是做语法分析的吧，你去参考下

Answer 2

import java.util.Stack;
public class Calcu{
Stack <Integer>num;
Stack <String>exp;
String expression="7+(8+2*2)/3-1=";
public Calcu(){
num=new Stack<Integer>();
exp=new Stack<String>();
}
public void calculate(){
char t;
int s;
int len=expression.length();
for(int i=0;i<len;i++){
t=expression.charAt(i);
switch(t){
case '-':
case '+':if(!exp.empty()&& !exp.peek().equals("(") && !exp.peek().equals(")")){
s=compute(exp.pop());
num.push(s);
} exp.push(String.valueOf(t));
break;
case '/':
case '*':
if(!exp.empty()&& exp.peek().equals("/")){
compute(exp.pop());
}else if(!exp.empty() && exp.peek().equals("*")){compute(exp.pop());}
else exp.push(String.valueOf(t));break;
case '(':exp.push(String.valueOf(t));break;
case ')':{
while(!exp.peek().equals("(")){
s=compute(exp.pop());
num.push(s);
}
exp.pop();
break;
}
case '=':{
while(!exp.empty()){
s=compute(exp.pop());
num.push(s);
}
System.out.println(num.pop());
break;
}
default:num.push(t-48);
}
}
}
private int compute(String exp){
int n2=num.pop();
int n1=num.pop();
switch(exp.charAt(0)){
case '+':return n1+n2;
case '-':return n1-n2;
case '*':return n1*n2;
case '/':return n1/n2;
}
return -1;
}
public static void main(String args[]){
Calcu c=new Calcu();
c.calculate();
}
}

Answer 3

上面的代码有点小问题。。
import java.util.Stack;
public class Calcu{
Stack <Integer>num;
Stack <String>exp;
String expression="7+(8+2*2)/3-1=";
public Calcu(){
num=new Stack<Integer>();
exp=new Stack<String>();
}
public void calculate(){
char t;
int s;
int len=expression.length();
for(int i=0;i<len;i++){
t=expression.charAt(i);
switch(t){
case '-':
case '+':if(!exp.empty()&& !exp.peek().equals("(") && !exp.peek().equals(")")){
s=compute(exp.pop());
num.push(s);
} exp.push(String.valueOf(t));
break;
case '/':
case '*':
if(!exp.empty()&& exp.peek().equals("/")){
s=compute(exp.pop());
num.push(s);
}else if(!exp.empty() && exp.peek().equals("*")){
s=compute(exp.pop());
num.push(s);
}
exp.push(String.valueOf(t));break;
case '(':exp.push(String.valueOf(t));break;
case ')':{
while(!exp.peek().equals("(")){
s=compute(exp.pop());
num.push(s);
}
exp.pop();
break;
}
case '=':{
while(!exp.empty()){
s=compute(exp.pop());
num.push(s);
}
System.out.println(num.pop());
break;
}
default:num.push(t-48);
}
}
}
private int compute(String exp){
int n2=num.pop();
int n1=num.pop();
switch(exp.charAt(0)){
case '+':return n1+n2;
case '-':return n1-n2;
case '*':return n1*n2;
case '/':return n1/n2;
}
return -1;
}
public static void main(String args[]){
Calcu c=new Calcu();
c.calculate();
}
}

Answer 4

给你逆波兰式算法.经过测试
package expression;    
   
import java.io.*;    
import java.util.*;    
   
public class Expression {    
    private ArrayList expression = new ArrayList();// 存储中序表达式    
   
    private ArrayList right = new ArrayList();// 存储右序表达式    
   
    private String result;// 结果    
   
    // 依据输入信息创建对象，将数值与操作符放入ArrayList中    
    private Expression(String input) {    
        StringTokenizer st = new StringTokenizer(input, "+-*/()", true);    
        while (st.hasMoreElements()) {    
            expression.add(st.nextToken());    
        }    
    }    
   
    // 将中序表达式转换为右序表达式    
    private void toRight() {    
        Stacks aStack = new Stacks();    
        String operator;    
        int position = 0;    
        while (true) {    
            if (Calculate.isOperator((String) expression.get(position))) {    
                if (aStack.top == -1   
                        || ((String) expression.get(position)).equals("(")) {    
                    aStack.push(expression.get(position));    
                } else {    
                    if (((String) expression.get(position)).equals(")")) {    
                        if (!((String) aStack.top()).equals("(")) {    
                            operator = (String) aStack.pop();    
                            right.add(operator);    
                        }    
                    } else {    
                        if (Calculate.priority((String) expression    
                                .get(position)) <= Calculate    
                                .priority((String) aStack.top())    
                                && aStack.top != -1) {    
                            operator = (String) aStack.pop();    
                            if (!operator.equals("("))    
                                right.add(operator);    
                        }    
                        aStack.push(expression.get(position));    
                    }    
                }    
            } else   
                right.add(expression.get(position));    
            position++;    
            if (position >= expression.size())    
                break;    
        }    
        while (aStack.top != -1) {    
            operator = (String) aStack.pop();    
            right.add(operator);    
        }    
    }    
   
    // 对右序表达式进行求值    
    private void getResult() {    
        this.toRight();    
        Stacks aStack = new Stacks();    
        String op1, op2, is = null;    
        Iterator it = right.iterator();    
   
        while (it.hasNext()) {    
            is = (String) it.next();    
            if (Calculate.isOperator(is)) {    
                op1 = (String) aStack.pop();    
                op2 = (String) aStack.pop();    
                aStack.push(Calculate.twoResult(is, op1, op2));    
            } else   
                aStack.push(is);    
        }    
        result = (String) aStack.pop();    
        it = expression.iterator();    
        while (it.hasNext()) {    
            System.out.print((String) it.next());    
        }    
        System.out.println("=" + result);    
    }    
   
    public static void main(String avg[]) {    
        try {    
            System.out.println("Input a expression:");    
            BufferedReader is = new BufferedReader(new InputStreamReader(    
                    System.in));    
            for (;;) {    
                String input = new String();    
                input = is.readLine().trim();    
                if (input.equals("q"))    
                    break;    
                else {    
                    Expression boya = new Expression(input);    
                    boya.getResult();    
                }    
                System.out    
                        .println("Input another expression or input 'q' to quit:");    
            }    
            is.close();    
        } catch (IOException e) {    
            System.out.println("Wrong input!!!");    
        }    
    }    
}     java 代码
package expression;    
   
public class Calculate {    
    // 判断是否为操作符号    
    public static boolean isOperator(String operator) {    
        if (operator.equals("+") || operator.equals("-")    
                || operator.equals("*") || operator.equals("/")    
                || operator.equals("(") || operator.equals(")"))    
            return true;    
        else   
            return false;    
    }    
   
    // 设置操作符号的优先级别    
    public static int priority(String operator) {    
        if (operator.equals("+") || operator.equals("-")    
                || operator.equals("("))    
            return 1;    
        else if (operator.equals("*") || operator.equals("/"))    
            return 2;    
        else   
            return 0;    
    }    
   
    // 做2值之间的计算    
    public static String twoResult(String operator, String a, String b) {    
        try {    
            String op = operator;    
            String rs = new String();    
            double x = Double.parseDouble(b);    
            double y = Double.parseDouble(a);    
            double z = 0;    
            if (op.equals("+"))    
                z = x + y;    
            else if (op.equals("-"))    
                z = x - y;    
            else if (op.equals("*"))    
                z = x * y;    
            else if (op.equals("/"))    
                z = x / y;    
            else   
                z = 0;    
            return rs + z;    
        } catch (NumberFormatException e) {    
            System.out.println("input has something wrong!");    
            return "Error";    
        }    
    }    
}    java 代码
package expression;     
import java.util.*;     
//栈类     
public class Stacks{     
   private LinkedList list=new LinkedList();     
   int top=-1;     
   public void push(Object value){     
      top++;     
      list.addFirst(value);     
   }     
   public Object pop(){     
      Object temp=list.getFirst();     
      top--;     
      list.removeFirst();     
      return temp;     
   
   }     
   public Object top(){     
   return list.getFirst();     
   }     
}     

Answer 5

package expression;    
   
import java.io.*;    
import java.util.*;    
   
public class Expression {    
    private ArrayList expression = new ArrayList();// 存储中序表达式    
   
    private ArrayList right = new ArrayList();// 存储右序表达式    
   
    private String result;// 结果    
   
    // 依据输入信息创建对象，将数值与操作符放入ArrayList中    
    private Expression(String input) {    
        StringTokenizer st = new StringTokenizer(input, "+-*/()", true);    
        while (st.hasMoreElements()) {    
            expression.add(st.nextToken());    
        }    
    }    
   
    // 将中序表达式转换为右序表达式    
    private void toRight() {    
        Stacks aStack = new Stacks();    
        String operator;    
        int position = 0;    
        while (true) {    
            if (Calculate.isOperator((String) expression.get(position))) {    
                if (aStack.top == -1   
                        || ((String) expression.get(position)).equals("(")) {    
                    aStack.push(expression.get(position));    
                } else {    
                    if (((String) expression.get(position)).equals(")")) {    
                        if (!((String) aStack.top()).equals("(")) {    
                            operator = (String) aStack.pop();    
                            right.add(operator);    
                        }    
                    } else {    
                        if (Calculate.priority((String) expression    
                                .get(position)) <= Calculate    
                                .priority((String) aStack.top())    
                                && aStack.top != -1) {    
                            operator = (String) aStack.pop();    
                            if (!operator.equals("("))    
                                right.add(operator);    
                        }    
                        aStack.push(expression.get(position));    
                    }    
                }    
            } else   
                right.add(expression.get(position));    
            position++;    
            if (position >= expression.size())    
                break;    
        }    
        while (aStack.top != -1) {    
            operator = (String) aStack.pop();    
            right.add(operator);    
        }    
    }    
   
    // 对右序表达式进行求值    
    private void getResult() {    
        this.toRight();    
        Stacks aStack = new Stacks();    
        String op1, op2, is = null;    
        Iterator it = right.iterator();    
   
        while (it.hasNext()) {    
            is = (String) it.next();    
            if (Calculate.isOperator(is)) {    
                op1 = (String) aStack.pop();    
                op2 = (String) aStack.pop();    
                aStack.push(Calculate.twoResult(is, op1, op2));    
            } else   
                aStack.push(is);    
        }    
        result = (String) aStack.pop();    
        it = expression.iterator();    
        while (it.hasNext()) {    
            System.out.print((String) it.next());    
        }    
        System.out.println("=" + result);    
    }    
   
    public static void main(String avg[]) {    
        try {    
            System.out.println("Input a expression:");    
            BufferedReader is = new BufferedReader(new InputStreamReader(    
                    System.in));    
            for (;;) {    
                String input = new String();    
                input = is.readLine().trim();    
                if (input.equals("q"))    
                    break;    
                else {    
                    Expression boya = new Expression(input);    
                    boya.getResult();    
                }    
                System.out    
                        .println("Input another expression or input 'q' to quit:");    
            }    
            is.close();    
        } catch (IOException e) {    
            System.out.println("Wrong input!!!");    
        }    
    }    
}     java 代码
package expression;    
   
public class Calculate {    
    // 判断是否为操作符号    
    public static boolean isOperator(String operator) {    
        if (operator.equals("+") || operator.equals("-")    
                || operator.equals("*") || operator.equals("/")    
                || operator.equals("(") || operator.equals(")"))    
            return true;    
        else   
            return false;    
    }    
   
    // 设置操作符号的优先级别    
    public static int priority(String operator) {    
        if (operator.equals("+") || operator.equals("-")    
                || operator.equals("("))    
            return 1;    
        else if (operator.equals("*") || operator.equals("/"))    
            return 2;    
        else   
            return 0;    
    }    
   
    // 做2值之间的计算    
    public static String twoResult(String operator, String a, String b) {    
        try {    
            String op = operator;    
            String rs = new String();    
            double x = Double.parseDouble(b);    
            double y = Double.parseDouble(a);    
            double z = 0;    
            if (op.equals("+"))    
                z = x + y;    
            else if (op.equals("-"))    
                z = x - y;    
            else if (op.equals("*"))    
                z = x * y;    
            else if (op.equals("/"))    
                z = x / y;    
            else   
                z = 0;    
            return rs + z;    
        } catch (NumberFormatException e) {    
            System.out.println("input has something wrong!");    
            return "Error";    
        }    
    }    
}    java 代码
package expression;     
import java.util.*;     
//栈类     
public class Stacks{     
   private LinkedList list=new LinkedList();     
   int top=-1;     
   public void push(Object value){     
      top++;     
      list.addFirst(value);     
   }     
   public Object pop(){     
      Object temp=list.getFirst();     
      top--;     
      list.removeFirst();     
      return temp;     
   
   }     
   public Object top(){     
   return list.getFirst();     
   }     
}