BlueJ字符串条件错误

Question

我的BlueJ在条件语句if中运行了错误的行。我的程序是：

import java.io.*;
public class version_check
{
    public static void main(String args[])throws IOException
    {
        BufferedReader read=new BufferedReader(new InputStreamReader(System.in));
        System.out.println("Enter your BlueJ version");
        String version=read.readLine();
        if(version!="3.1.1")
        System.out.println("You need to upgrade your BlueJ version");
        else
        System.out.println("You have the latest BlueJ version");
    }
}

输出屏幕：

Enter your BlueJ version
3.1.1
You need to upgrade your BlueJ version

我犯了什么错误？

Answer 1

使用.equals比较字符串。

if(version!="3.1.1")   
        System.out.println("You need to upgrade your BlueJ version");  

至

if(!(version.equals("3.1.1")))   
        System.out.println("You need to upgrade your BlueJ version");  

Answer 2

我所知道的字符串类型的比较方法只有: 1.>String_variable.equals(String_to_be_checked_with)和2.>String_variable.equalsIgnoresCase(String_to_be_checked_with)

第二个忽略已输入的字符串值的大小写...

对您的问题最简单的解决方案是：

if(version.equals("3.1.1"))
{
    System.out.println("You have the latest BlueJ version");        

}
else {
    System.out.println("You need to upgrade your BlueJ version");
}

Answer 3

     import java.io.*;
     public class version_check
      {
        public static void main(String args[])throws IOException
         {
          BufferedReader read=new BufferedReader(new 
     InputStreamReader(System.in));
       System.out.println("Enter your BlueJ version");
        String version=read.readLine();
       if(!version.equals ("3.1.1"))
          System.out.println("You need to upgrade your BlueJ 
       version");
    else
         System.out.println ("You have the latest BlueJ version");
            }
           }