开发实例：利用java做一个简单的计算器
两个类。还只是完成＋、－、×、÷运算而已。GUI只是用了AWT，很简单，相信一看就能懂了。
Calculator.java
以下是引用片段：
publicclassCalculator{
privateStringresult="0";
privateintop=0,add=1,sub=2,mul=3,div=4;
privatedoublestringToDouble(Stringx){
doubley=Double.parseDouble(x);
returny;
}
privatevoidoperate(Stringx){
doublex1=stringToDouble(x);
doubley=stringToDouble(result);
switch(op){
case0:
result=x;
break;
case1:
result=String.valueOf(y x1);
break;
case2:
result=String.valueOf(y-x1);
break;
case3:
result=String.valueOf(y*x1);
break;
case4:
if(x1!=0){
result=String.valueOf(y/x1);
}else{
result="Thedivisorcan'tbezero!";
}
break;
}
}
publicStringopAdd(Stringx){
operate(x);
op=add;
returnresult;
}
publicStringopSubtract(Stringx){
operate(x);
op=sub;
returnresult;
}
publicStringopMultiply(Stringx){
operate(x);
op=mul;
returnresult;
}
publicStringopDivide(Stringx){
operate(x);
op=div;
returnresult;
}
publicStringopEquals(Stringx){
operate(x);
op=0;
returnresult;
}
publicvoidopClean(){
op=0;
result="0";
}
}
第二个
CalculatorGUI.java
以下是引用片段：
importjava.awt.*;
importjava.awt.event.*;
importjava.util.EventObject;
publicclassCalculatorGUI{
privateFramef;
privatePanelp1,p2;
privateButtonb0,b1,b2,b3,b4,b5,b6,b7,b8,b9;
privateButtonbPoint,bAdd,bDec,bMul,bDiv,bCal;
privateTextFieldtf;
privateStrings,op;
privateCalculatorcal=newCalculator();
privatebooleanifOp;
publicCalculatorGUI(){
f=newFrame("Calculator");
p1=newPanel();
p2=newPanel();
b0=newButton("0");
b1=newButton("1");
b2=newButton("2");
b3=newButton("3");
b4=newButton("4");
b5=newButton("5");
b6=newButton("6");
b7=newButton("7");
b8=newButton("8");
b9=newButton("9");
bPoint=newButton(".");
bAdd=newButton(" ");
bDec=newButton("-");
bMul=newButton("*");
bDiv=newButton("/");
bCal=newButton("=");
tf=newTextField(25);
tf.setEditable(false);
}
publicvoidlaunchFrame(){
f.setSize(220,160);
f.setResizable(false);
f.addWindowListener(newmyWindowListener());
p1.setLayout(newFlowLayout(FlowLayout.CENTER));
p1.add(tf);
f.add(p1,BorderLayout.NORTH);
p2.setLayout(newGridLayout(4,4));
b0.addActionListener(newsetLabelText_ActionListener());
b1.addActionListener(newsetLabelText_ActionListener());
b2.addActionListener(newsetLabelText_ActionListener());
b3.addActionListener(newsetLabelText_ActionListener());
b4.addActionListener(newsetLabelText_ActionListener());
b5.addActionListener(newsetLabelText_ActionListener());
b6.addActionListener(newsetLabelText_ActionListener());
b7.addActionListener(newsetLabelText_ActionListener());
b8.addActionListener(newsetLabelText_ActionListener());
b9.addActionListener(newsetLabelText_ActionListener());
bPoint.addActionListener(newsetLabelText_ActionListener());
bAdd.addActionListener(newsetOperator_ActionListener());
bDec.addActionListener(newsetOperator_ActionListener());
bMul.addActionListener(newsetOperator_ActionListener());
bDiv.addActionListener(newsetOperator_ActionListener());
bCal.addActionListener(newsetOperator_ActionListener());
p2.add(b7);
p2.add(b8);
p2.add(b9);
p2.add(bAdd);
p2.add(b4);
p2.add(b5);
p2.add(b6);
p2.add(bDec);
p2.add(b1);
p2.add(b2);
p2.add(b3);
p2.add(bMul);
p2.add(b0);
p2.add(bPoint);
p2.add(bCal);
p2.add(bDiv);
f.add(p2,BorderLayout.SOUTH);
f.setVisible(true);
}
publicvoidsetTextFieldText_Temp(){
if(tf.getText().length()<15&&(tf.getText().indexOf(".")==-1||!s.equals("."))){
tf.setText(tf.getText() s);
}else{
tf.setText((tf.getText() s).substring(0,15));
}
}
publicvoidsetTextFieldText(){
if(ifOp){
ifOp=false;
tf.setText("");
setTextFieldText_Temp();
}else{
setTextFieldText_Temp();
}
}
publicstaticvoidmain(String[]args){
CalculatorGUIcalculator=newCalculatorGUI();
calculator.launchFrame();
}
classmyWindowListenerextendsWindowAdapter{
publicvoidwindowClosing(WindowEvente){
System.exit(0);
}
}
classsetLabelText_ActionListenerimplementsActionListener{
publicvoidactionPerformed(ActionEvente){
ButtontempB=(Button)e.getSource();
s=tempB.getLabel();
setTextFieldText();
}
}
classsetOperator_ActionListenerimplementsActionListener{
publicvoidactionPerformed(ActionEvente){
ButtontempB=(Button)e.getSource();
op=tempB.getLabel();
if(op.equals(" ")){
tf.setText(cal.opAdd(tf.getText()));
ifOp=true;
}elseif(op.equals("-")){
tf.setText(cal.opSubtract(tf.getText()));
ifOp=true;
}elseif(op.equals("*")){
tf.setText(cal.opMultiply(tf.getText()));
ifOp=true;
}elseif(op.equals("/")){
tf.setText(cal.opDivide(tf.getText()));
ifOp=true;
}elseif(op.equals("=")){
tf.setText(cal.opEquals(tf.getText()));
ifOp=true;
}
}
}
}
