Java If/else语句

我几天前刚刚开始使用java。我目前正在学习这门课程。我还没有遇到任何问题，但现在我被任务32困住了

以下是我到目前为止的代码（总是以Squirrel而不是moose作为输出）：

公开课问题32{

public static void main(String[] args) {
    boolean animal, vegetable, mineral, smallerthan;

    String whatIsIt, biggerThan;
    Scanner keyboard = new Scanner(System.in);


    System.out.println("Hello and welcome, i've got 2 questions for you!");
    System.out.println("Think of an object and i'll try to guess it");
    System.out.println();
    System.out.println("Question 1) Is it an animal, vegetable or mineral?");
    System.out.print(">");
    whatIsIt = keyboard.nextLine();

    if (whatIsIt == "animal")
            animal = true;
            if (whatIsIt == "vegetable")
            vegetable = true;
            if (whatIsIt == "mineral")
            mineral = true;


    System.out.println("Question 2) Is it bigger than a breadbox?");
    System.out.print(">");
        biggerThan = keyboard.nextLine();
            if (biggerThan == "yes")
            smallerthan = false;
            if (biggerThan == "no"){
            smallerthan = true;}


            System.out.print("My guess is that you are thinking of a ");
        if (animal = true){
            if (smallerthan = true)
                System.out.println("squirrel");
        }else { 
                System.out.println("moose");}
}   
}

提前谢谢！我也很想听听如何以更智能的方式编写代码的提示。友好一点，记住我才刚刚开始

编辑：好的，我采取了另一种方法。我的第一次尝试真的很奇怪。谢谢你的帮助

工作代码如下：

import java.util.Scanner;

公开课问题32{

public static void main(String[] args) {
    Scanner keyboard = new Scanner(System.in);


    String whatIsIt, whatIsIt2;
    String animal = "animal";
    String mineral = "mineral";
    String vegetable = "vegetable";
    String bigger = "yes";
    String smaller = "no";


    System.out.println("Hello and welcome, i've got 2 questions for you!");
    System.out.println("Think of an object and i'll try to guess it");
    System.out.println();
    System.out.println("Question 1) Is it an animal, vegetable or mineral?");
    System.out.print(">");
    whatIsIt = keyboard.nextLine();

    System.out.println("Question 2) Is it bigger than a breadbox?");
    System.out.print(">");
        whatIsIt2 = keyboard.nextLine();

    if (whatIsIt.equalsIgnoreCase(animal)){
        if (whatIsIt2.equalsIgnoreCase(bigger)){
            System.out.println("My guess is that you are thinking of a moose");
        }else{ System.out.println("My guess is that you are thinking of a squirrel");
        }
    }

    if (whatIsIt.equalsIgnoreCase(vegetable)){
        if (whatIsIt2.equalsIgnoreCase(bigger)){
            System.out.println("My guess is that you are thinking of a melon");
        }else{ System.out.println("My guess is that you are thinking of a carrot");
        }
    }

    if (whatIsIt.equalsIgnoreCase(mineral)){
        if (whatIsIt2.equalsIgnoreCase(bigger)){
            System.out.println("My guess is that you are thinking of a Camaro");
        }else{ System.out.println("My guess is that you are thinking of a paper clip");
        }
    }
    System.out.println("I would ask you if I'm right, but I dont actually care.");

    }


}

---

在if语句中，您每次都将animal设置为true

if（animal=true）{

，而不是检查它（

=

）。

---

另外，对于字符串，您必须使用

.equals（）

而不是

=

不要将字符串与

=

或

！=

进行比较。请理解，这会比较引用--两个字符串变量引用相同的字符串对象，而这不是您想要的。请使用字符串

equals（…）

或其

等效信号情况（…）

执行函数相等性测试的方法—字符串具有相同顺序的相同字符—这正是您想要的。还要了解赋值和关系相等性之间的差异。另外，还要了解yoda表达式。即使只有凌晨3点的调试会话会永久性地加强这种差异。不确定您使用的是什么IDE，但您应该得到一个关于在if条件内执行赋值的大警告。忽略这些警告肯定会引入错误，特别是对于初学者来说。好的，equalsIgnoreCase（…）工作得很好。对于“在if条件内不执行赋值”，我仍然有点困惑.所以通过我这样做的方式，我总是将布尔值设置为真？绕过它的最佳方式是什么？顺便说一句，我使用Eclipse和1.8，我没有收到任何关于这些问题的警告

public static void main(String[] args) {
    Scanner keyboard = new Scanner(System.in);


    String whatIsIt, whatIsIt2;
    String animal = "animal";
    String mineral = "mineral";
    String vegetable = "vegetable";
    String bigger = "yes";
    String smaller = "no";


    System.out.println("Hello and welcome, i've got 2 questions for you!");
    System.out.println("Think of an object and i'll try to guess it");
    System.out.println();
    System.out.println("Question 1) Is it an animal, vegetable or mineral?");
    System.out.print(">");
    whatIsIt = keyboard.nextLine();

    System.out.println("Question 2) Is it bigger than a breadbox?");
    System.out.print(">");
        whatIsIt2 = keyboard.nextLine();

    if (whatIsIt.equalsIgnoreCase(animal)){
        if (whatIsIt2.equalsIgnoreCase(bigger)){
            System.out.println("My guess is that you are thinking of a moose");
        }else{ System.out.println("My guess is that you are thinking of a squirrel");
        }
    }

    if (whatIsIt.equalsIgnoreCase(vegetable)){
        if (whatIsIt2.equalsIgnoreCase(bigger)){
            System.out.println("My guess is that you are thinking of a melon");
        }else{ System.out.println("My guess is that you are thinking of a carrot");
        }
    }

    if (whatIsIt.equalsIgnoreCase(mineral)){
        if (whatIsIt2.equalsIgnoreCase(bigger)){
            System.out.println("My guess is that you are thinking of a Camaro");
        }else{ System.out.println("My guess is that you are thinking of a paper clip");
        }
    }
    System.out.println("I would ask you if I'm right, but I dont actually care.");

    }


}