如果else语句给出了错误的输出[duplicate]

Question

我正在尝试通过使用if else条件在我的代码中的textbox上添加验证

我在textbox上添加了focusListener，当我从textbox中删除焦点时，它将检查条件
我还在chekbox旁边创建了一个标签，它将根据条件显示文本

如果textbox中的文本不等于“Hi”，则应在textbox旁边的标签中打印“Hello

否则应打印“再见”

import java.awt.*;  
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.FocusAdapter;
import java.awt.event.FocusEvent;
import javax.swing.*;

public class regframe extends JFrame implements ActionListener
{
    
    private static final long serialVersionUID = 1L;
    JTextField t1,t2;
    JLabel l1,l2,l3,l4;
    JButton b;

    regframe()
    {   
        getContentPane().setBackground(Color.BLACK);
        l1=new JLabel("Enter First Num:");
        l1.setBounds(50,50,150,20);
        l1.setForeground(Color.WHITE);
        l1.setFont(new Font("Verdana",Font.BOLD,12));
        add(l1);

        t1=new JTextField();
        t1.setBounds(180,50,100,20);
        t1.setBackground(Color.BLACK);
        t1.setForeground(Color.WHITE);
        t1.setBorder(BorderFactory.createMatteBorder(0, 0, 1, 0,Color.YELLOW));
        t1.setCaretColor(Color.CYAN);
        t1.setFont(new Font("Verdana",Font.BOLD,12));
        t1.addActionListener(this);
        add(t1);
        
        l3=new JLabel();
        l3.setBounds(290,50,150,20);
        l3.setForeground(Color.CYAN);
        l3.setOpaque(false);
        l3.setFont(new Font("Verdana",Font.BOLD,10));
        add(l3);

        t1.addFocusListener(new FocusAdapter() 
        {
            public void focusLost(FocusEvent e)
            {
                if(t1.getText()!="hi")
                {
                    l3.setText("hello");
                }
                else
                {
                    l3.setText("bye");
                }
            }
        });
        

        l2=new JLabel("Enter Second Num:");
        l2.setBounds(50,80,150,20);
        l2.setForeground(Color.WHITE);
        l2.setFont(new Font("Verdana",Font.BOLD,12));
        add(l2);        

        t2=new JTextField();
        t2.setBounds(180,80,100,20);
        t2.setBackground(Color.BLACK);
        t2.setForeground(Color.WHITE);
        t2.setBorder(BorderFactory.createMatteBorder(0, 0, 1, 0,Color.YELLOW));
        t2.setCaretColor(Color.CYAN);
        t2.setFont(new Font("Verdana",Font.BOLD,12));
        add(t2);
                
        b=new JButton("Submit");
        b.setBounds(100,120,100,20);
        b.setBackground(Color.CYAN);
            b.setForeground(Color.BLACK);
        add(b);

        setLocation(300,200);
        setSize(700,250);
        setLayout(null);
        setTitle("Registration");
        setVisible(true);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        
    }
    
    public static void main(String args[])
    {
        new regframe();
    }

    public void actionPerformed(ActionEvent arg0) 
    {
        
        
    }
}

请帮忙

Answer 1

使用

if(!"hi".equals(t1.getText()) 

而不是

if(t1.getText()!="hi")

您还可以执行if（！t1.getText().equals（“hi”）），但另一个方法更适合空

查看https://www.javatpoint.com/string-comparis-in-