简易Java控制台计算器

最新推荐文章于 2022-10-12 11:10:20 发布

CodingMouse

最新推荐文章于 2022-10-12 11:10:20 发布

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简易Java控制台计算器

源码清单：

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!!!");

}

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";

}

// 栈类

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();

}