200行Java代码编写一个计算器程序

200行Java代码编写一个计算器程序

发现了大学时候写的计算器小程序，还有个图形界面，能够图形化展示表达式语法树，哈哈;)

只有200行java代码，不但能够计算加减乘除，还能够匹配小括号~

代码点评：

实现代码如下所示：

import java.awt.BorderLayout;

import java.awt.Color;

import java.awt.Graphics;

import java.awt.Point;

import java.awt.TextField;

import java.awt.event.KeyAdapter;

import java.awt.event.KeyEvent;

import java.util.Stack;

import javax.swing.JFrame;

/** * 图形界面的计算器程序，只能计算加减乘除， * 算式中可以有小括号。数字可以是小数 */

public class CalcGUI extends JFrame{

private static final long serialVersionUID = 1L;

private TreeNode resultTree;

private String textFieldString;

private boolean calcSuccess = true;

private char ops[][] = {

{'>', '>', '<', '<', '<', '>', '>'},

{'>', '>', '<', '<', '<', '>', '>'},

{'>', '>', '>', '>', '<', '>', '>'},

{'>', '>', '>', '>', '<', '>', '>'},

{'<', '<', '<', '<', '<', '=', 'E'},

{'E', 'E', 'E', 'E', 'E', 'E', 'E'},

{'<', '<', '<', '<', '<', 'E', '='},

};

Stack nodesStack = new Stack();

Stack opsStack = new Stack();

publicstaticvoidmain(String[] args) {

CalcGUI gui = new CalcGUI();

gui.userGUI();

}

publicvoiduserGUI(){

this.setLayout(new BorderLayout());

TextField tf = new TextField("请输入表达式，按Enter开始计算~", 40);

tf.selectAll();

tf.getText();

tf.addKeyListener(new KeyAdapter(){

publicvoidkeyPressed(KeyEvent e){

if(e.getKeyCode() == KeyEvent.VK_ENTER){

textFieldString = ((TextField)e.getComponent()).getText();

calcSuccess = true;

resultTree = null;

try{

resultTree = calc(textFieldString + "#");

}catch(Exception e1){

calcSuccess = false;

}

CalcGUI.this.repaint();

}

}

});

this.add(tf, BorderLayout.NORTH);

this.setSize(500, 500);

this.setTitle("calc GUI");

this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

this.setResizable(true);

this.setVisible(true);

}

private int levelHeight = 60;

private int diameter = 25;

publicvoidpaint(Graphics g){

super.paint(g);

if(calcSuccess){

if(resultTree != null){

g.drawString("计算结果为：" + resultTree.value, 10, 80);

int rootBeginX = this.getWidth() / 2;

int rootBeginY = 100;

Point p = new Point(rootBeginX, rootBeginY);

drawTree(g, resultTree, p, this.getWidth() / 2 - 20, p);

}

}else{

g.setColor(Color.RED);

g.drawString("表达式语法有误！", 10, 80);

}

}

privatevoiddrawCircle(Graphics g, Point p, int r){

g.drawOval(p.x - r, p.y - r, r * 2, r * 2);

}

privatevoiddrawTree(Graphics g, TreeNode node, Point pme, int width, Point pfather){

if(node == null) return;

// System.out.println("in drawTree, node.value=" + node.value + ",node.op=" + node.op);

g.setColor(Color.GREEN);

this.drawCircle(g, pme, diameter / 2);

g.drawLine(pme.x, pme.y, pfather.x, pfather.y);

if(node.op != 'E'){

g.setColor(Color.BLACK);

g.drawString(String.valueOf(node.op), pme.x, pme.y);

}else{

g.setColor(Color.BLACK);

g.drawString(String.valueOf(node.value), pme.x - diameter / 2, pme.y);

}

drawTree(g, node.lft, new Point(pme.x - width / 2, pme.y + levelHeight), width / 2, pme);

drawTree(g, node.rt, new Point(pme.x + width / 2, pme.y + levelHeight), width / 2, pme);

}

public TreeNode calc(String inStr) throws Exception{

opsStack.push('#');

StringBuilder buf = new StringBuilder();

int i = 0;

while(i < inStr.length()){

if(Character.isDigit(inStr.charAt(i)) || inStr.charAt(i) == '.'){// number

buf.delete(0, buf.length());

while(i < inStr.length() &&

(Character.isDigit(inStr.charAt(i)) || inStr.charAt(i) == '.'))

buf.append(inStr.charAt(i++));

Double number = Double.parseDouble(buf.toString());

nodesStack.push(new TreeNode(number));

}else if(inStr.charAt(i) == ' '){

i++;

continue;

}else{// operation

char op = inStr.charAt(i);

int subNew = getSub(op);

boolean goOn = true;

while(goOn){

if(opsStack.isEmpty())

throw new Exception("运算符太少！");

char opFormer = opsStack.peek();

int subFormer = getSub(opFormer);

switch(ops[subFormer][subNew]){

case '=':

goOn = false;

opsStack.pop();

break;

case '<':

goOn = false;

opsStack.push(op);

break;

case '>':

goOn = true;

TreeNode n1 = nodesStack.pop();

TreeNode n0 = nodesStack.pop();

double rs = doOperate(n0.value, n1.value, opFormer);

nodesStack.push(new TreeNode(rs, opFormer, n0, n1));

opsStack.pop();

break;

default:

throw new Exception("没有匹配的操作符：" + op);

}

}

i++;

}

}

return nodesStack.pop();

}

privatedoubledoOperate(double n0, double n1, char op) throws Exception{

switch(op){

case '+': return n0 + n1;

case '-': return n0 - n1;

case '*': return n0 * n1;

case '/': return n0 / n1;

default: throw new Exception("非法操作符：" + op);

}

}

privateintgetSub(char c){

switch(c){

case '+': return 0;

case '-': return 1;

case '*': return 2;

case '/': return 3;

case '(': return 4;

case ')': return 5;

case '#': return 6;

default : return -1;

}

}

}

class TreeNode{

public double value;

public char op = 'E';

public TreeNode lft;

public TreeNode rt;

public TreeNode(double value){

this.value = value;

}

public TreeNode(double value, char op, TreeNode lft, TreeNode rt){

this.value = value;

this.op = op;

this.lft = lft;

this.rt = rt;

}

StringBuilder buf = new StringBuilder();

public String toString(){

out(this);

return buf.toString();

}

privatevoidout(TreeNode node){

if(node == null) return;

out(node.lft);

if(node.op != 'E')

buf.append(node.op);

else

buf.append(node.value);

out(node.rt);

}

}

总结

以上所述是给大家介绍的200行Java代码编写一个计算器程序，希望对大家有所帮助，如果大家有任何疑问请给我留言，会及时回复大家的。在此也非常感谢大家对我们的支持！

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