没做完的计算器，ActionListener下面的if语句不跑啊 求解释啊。。。
import java.applet.*;
import java.awt.*;
import java.awt.event.*;
public class UseArithmetic extends Applet {



Label prompt,result;
TextField input1,input2,input3;
Button btn0,btn1, btn2, btn3, btn4, btn5, btn6, btn7, btn8, btn9, btn10, btn11, btn12, btn13,btn14;
int a=2, b=1,d=3;
String c="";
public void init( )
{
result=new Label("");
prompt = new Label("输入");
input1 = new TextField(5);
input2 = new TextField(5);
input3 = new TextField(5);  
btn0= new Button("0");
btn1= new Button("1");
btn2= new Button("2");
btn3= new Button("3");
btn4= new Button("4");
btn5= new Button("5");
btn6= new Button("6");
btn7= new Button("7");
btn8= new Button("8");
btn9= new Button("9");
btn10= new Button("+");
btn11= new Button("-");
btn12= new Button("*");
btn13= new Button("/");
btn14=new Button("=");
add(result);
add(prompt);
add(input1);
add(input2);
add(input3);
add(btn0);
add(btn1);
add(btn2);
add(btn3);
add(btn4);
add(btn5);
add(btn6);
add(btn7);
add(btn8);
add(btn9);
add(btn10);
add(btn11);
add(btn12);
add(btn13);
add(btn14);
btn0.addActionListener(new BtnActionAdapter());
btn1.addActionListener(new BtnActionAdapter());
btn2.addActionListener(new BtnActionAdapter());
btn3.addActionListener(new BtnActionAdapter());
btn4.addActionListener(new BtnActionAdapter());
btn5.addActionListener(new BtnActionAdapter());
btn6.addActionListener(new BtnActionAdapter());
btn7.addActionListener(new BtnActionAdapter());
btn8.addActionListener(new BtnActionAdapter());
btn9.addActionListener(new BtnActionAdapter());
btn10.addActionListener(new fuhaoActionAdapter());
btn11.addActionListener(new fuhaoActionAdapter());
btn12.addActionListener(new fuhaoActionAdapter());
btn13.addActionListener(new fuhaoActionAdapter());
btn14.addActionListener(new denghaoActionAdapter());
}
/* public void paint(Graphics g)
{

g.drawString("结果是："+d+a+b+c, 10, 130);
}
*/
 

class BtnActionAdapter implements ActionListener{
public void actionPerformed(ActionEvent e)
{
input1.setText(((Button)e.getSource()).getLabel());
input3.setText(((Button)e.getSource()).getLabel());
a = Integer.parseInt(input1.getText());
b= Integer.parseInt(input3.getText());



}
}
class fuhaoActionAdapter implements ActionListener{
public void actionPerformed(ActionEvent e)
{
input2.setText(((Button)e.getSource()).getLabel());
c=input2.getText();
}

 
}
class denghaoActionAdapter implements ActionListener{
public void actionPerformed(ActionEvent e)
{

int d=3;
if(c=="+") //这里它不跑
d=a+b;
else if(c=="-")
d=a-b;
else if(c=="*")
d=a*b;
else if(c=="/")
d=a/b;
result.setText(a+c+b+"="+d);
 
}

}

}

------解决方案--------------------
(c=="+") //这里它不跑，是什么意思？程序卡到这里？还有(c=="+") 改为("+".equals(c))
------解决方案--------------------
你也稍微把这些控件布局一下呀。。乱的一锅粥。。