简单 Java If 语句无法与 Sevlet 一起正常工作或 Java class

Question

我正在使用 eclipse Keplerr IDE 进行动态 Web 项目

出现的问题是，即使 java 条件 if 语句正确，简单且数据正确，它也不会返回 IF 语句的第一个（真）部分，即使它是真的。

我的代码：

GetSetClass（模型）

package tempTryOct15;


public class GetSetClass {

    String Conditionalz(String txt1){

        String t1 = txt1;
        System.out.println("The String Received is:" + t1);

        String ret="NULL-Value";
        if(t1=="ssc")
            ret="SSC";
        else
            ret="Non-SSC";

        System.out.println("returned: " + ret);
        return ret;
    }

}

tryServlet.java（控制器）

package tempTryOct15;

import java.io.IOException;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


/**
 * Servlet implementation class tryServlet
 */
public class tryServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public tryServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        String txt1=request.getParameter("txt1");
        String txt2=request.getParameter("txt2");

        System.out.println("The 1st String Entered is:" + txt1);
        System.out.println("The 2nd String Entered is:" + txt2);

        request.setAttribute("text1",txt1);

        /*
        GetSetClass GSC = new GetSetClass();
        String text2 = GSC.Conditionalz(txt1);
        System.out.println(text2);

        */

        if(txt1=="ssc")
            txt2="SSC";
        else
            txt2="Non-SSC";

        request.setAttribute("text2",txt2);

        System.out.println("The 2nd String Got is:" + txt2);

        RequestDispatcher view = request.getRequestDispatcher("Display.jsp");
            view.forward(request, response);

    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
    }

}

相同的代码在 core plain java 和 Notepad++ 编辑器上运行良好。如：

Try.java

class Try{

    String Conditionalz(String t1){

        System.out.println("The String Received is:" + t1);

        String ret="NULL-Value";
        if(t1=="ssc")
            ret="SSC";
        else
            ret="Non-SSC";

        return ret;
    }
}

TryDemo.java

class TryDemo{
    public static void main(String[] args){

        Try t = new Try();
        String ret = t.Conditionalz("ssc");
        System.out.println("returned: " + ret);

    }
}

Answer 1

由于 String 不是原始类型，因此您必须使用 str1.equals(str2) 而不是 str1==str2 ...

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