此代码中存在多个问题 - 类型：不匹配

Question

所以我编写了一个JAVA代码，该代码应该告诉用户如果将另外两个（从列表中）随机选择的颜色组合，他将获得什么颜色。请注意，我对JAVA很新（以前只用Python编程）。

代码：

    package ListOfWords;

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

      String [] colors = {"red","green","gray","black","blue","yellow"};

      int colorsLength = colors.length;

      int rand1 = (int) (Math.random() * colorsLength);
      int rand2 = (int) (Math.random() * colorsLength);

      while(rand1==rand2){
          int rand2 = (int) (Math.random() * colorsLength);
      }

      String phrase1 = colors[rand1];
      String phrase2 = colors[rand2];       

      while(phrase1 = "green"){

       if (phrase2 = "red") {
          System.out.print("Combining" + " " + phrase1 + " " + "with" + " " + phrase2 + " " + "will give you the color Brown");
        }
       if (phrase2 = "gray") {
          System.out.print("Combining" + " " + phrase1 + " " + "with" + " " + phrase2 + " " + "will give you the color Dark Green");
        }
       if (phrase2 = "black") {
          System.out.print("Combining" + " " + phrase1 + " " + "with" + " " + phrase2 + " " + "will give you the color Black");
        }
        if (phrase2 = "blue") {
            System.out.print("Combining" + " " + phrase1 + " " + "with" + " " + phrase2 + " " + "will give you the color Brown");
        }

        if (phrase2 = "yellow") {
            System.out.print("Combining" + " " + phrase1 + " " + "with" + " " + phrase2 + " " + "will give you the color Brown");
        }
        }
    while(phrase1 = "red"){

        if (phrase2 = "green") {
            System.out.print("Combining" + " " + phrase1 + " " + "with" + " " + phrase2 + " " + "will give you the color Brown");
        }
        if (phrase2 = "gray") {
            System.out.print("Combining" + " " + phrase1 + " " + "with" + " " + phrase2 + " " + "will give you the color Dark Red");
        }
        if (phrase2 = "black") {
            System.out.print("Combining" + " " + phrase1 + " " + "with" + " " + phrase2 + " " + "will give you the color Black");
        }
        if (phrase2 = "blue") {
            System.out.print("Combining" + " " + phrase1 + " " + "with" + " " + phrase2 + " " + "will give you the color Brown");
        }
        if (phrase2 = "yellow") {
            System.out.print("Combining" + " " + phrase1 + " " + "with" + " " + phrase2 + " " + "will give you the color Brown");
        }
     }
     while(phrase1 = "gray"){

        if (phrase2 = "red") {
        System.out.print("Combining" + " " + phrase1 + " " + "with" + " " + phrase2 + " " + "will give you the color Dark red");
        }
        if (phrase2 = "green") {
        System.out.print("Combining" + " " + phrase1 + " " + "with" + " " + phrase2 + " " + "will give you the color Dark Green");
        }
        if (phrase2 = "black") {
        System.out.print("Combining" + " " + phrase1 + " " + "with" + " " + phrase2 + " " + "will give you the color Black");
        }
        if (phrase2 = "blue") {
        System.out.print("Combining" + " " + phrase1 + " " + "with" + " " + phrase2 + " " + "will give you the Dark blue");
        }
        if (phrase2 = "yellow") {
        System.out.print("Combining" + " " + phrase1 + " " + "with" + " " + phrase2 + " " + "will give you the color Green");
        }
     }
     while(phrase1 = "black"){

        if (phrase2 = "red") {
            System.out.print("Combining" + " " + phrase1 + " " + "with" + " " + phrase2 + " " + "will give you the color Black");
        }
        if (phrase2 = "green") {
            System.out.print("Combining" + " " + phrase1 + " " + "with" + " " + phrase2 + " " + "will give you the color Black");
        }
        if (phrase2 = "gray") {
            System.out.print("Combining" + " " + phrase1 + " " + "with" + " " + phrase2 + " " + "will give you the color Black");
        }
        if (phrase2 = "blue") {
            System.out.print("Combining" + " " + phrase1 + " " + "with" + " " + phrase2 + " " + "will give you the Black");
        }
        if (phrase2 = "yellow") {
            System.out.print("Combining" + " " + phrase1 + " " + "with" + " " + phrase2 + " " + "will give you the color Black");
        }
     }
     while(phrase1 = "yellow"){

        if (phrase2 = "red") {
            System.out.print("Combining" + " " + phrase1 + " " + "with" + " " + phrase2 + " " + "will give you the color Brown");
        }
        if (phrase2 = "green") {
            System.out.print("Combining" + " " + phrase1 + " " + "with" + " " + phrase2 + " " + "will give you the color Blue");
        }
        if (phrase2 = "gray") {
            System.out.print("Combining" + " " + phrase1 + " " + "with" + " " + phrase2 + " " + "will give you the color Green");
        }
        if (phrase2 = "blue") {
            System.out.print("Combining" + " " + phrase1 + " " + "with" + " " + phrase2 + " " + "will give you the Green");
        }
        if (phrase2 = "black") {
            System.out.print("Combining" + " " + phrase1 + " " + "with" + " " + phrase2 + " " + "will give you the color Black");
        }
     }
     while(phrase1 = "Blue"){

        if (phrase2 = "red") {
            System.out.print("Combining" + " " + phrase1 + " " + "with" + " " + phrase2 + " " + "will give you the color Brown");
        }
        if (phrase2 = "green") {
            System.out.print("Combining" + " " + phrase1 + " " + "with" + " " + phrase2 + " " + "will give you the color Brown");
        }
        if (phrase2 = "gray") {
            System.out.print("Combining" + " " + phrase1 + " " + "with" + " " + phrase2 + " " + "will give you the Dark blue");
        }
        if (phrase2 = "yellow") {
            System.out.print("Combining" + " " + phrase1 + " " + "with" + " " + phrase2 + " " + "will give you the Green");
        }
        if (phrase2 = "black") {
            System.out.print("Combining" + " " + phrase1 + " " + "with" + " " + phrase2 + " " + "will give you the color Black");
        }
    }
}

}

所以我收到一条错误消息：

    Exception in thread "main" java.lang.Error: Unresolved compilation problems: 
    Duplicate local variable rand2
    Type mismatch: cannot convert from String to Boolean.

我不知道如何解决这个问题 - 请帮助。

Answer 1

首先=用于赋值，您必须使用==作为布尔运算符。

其次，要比较Java中的字符串，您需要在字符串上调用equals()方法。

if ("red".equals(phrase2)) {
    // logic here
}

第三，你分配了两次rand2。您必须第二次使用其他变量，或者必须删除int指示。

int rand2 = (int) (Math.random() * colorsLength);

while(rand1==rand2){
    rand2 = (int) (Math.random() * colorsLength);
}

Answer 2

你遇到的一个问题是：

while(rand1==rand2){
    int rand2 = (int) (Math.random() * colorsLength);
}

您已经宣布rand2，所以不要再这样做了。你应该把它改成：

while(rand1==rand2){
    rand2 = (int) (Math.random() * colorsLength);
}

另一件事是，您将赋值运算符（=）与等于运算符（==）混合。前者为变量赋值，后者检查变量是否相等。

当您尝试匹配变量时，请使用==。

最后，在Java中，您不能使用相等运算符来检查字符串 - 这将在字面上将一个对象与另一个对象匹配，并查看它们是否是同一个对象。您必须使用equals方法，如下所示：

while(phrase1.equals("green"))

而不是：

while(phrase1 = "green")

甚至while(phrase1 == "green")（适用于整数/布尔/其他类型）。

Answer 3

为了比较Java中的字符串，您必须使用equals（）方法使用"red".equals(phrase2)或"red".equalsIgnoreCase(phrase2)

Java中的

==运算符用于检查相等性，=是赋值运算符。但是Java中的字符串是String.class的对象所以==做引用检查而不是值检查。

因此，要比较Java中的两个对象，请使用equals()方法。

Answer 4

这里有一个语法错误：

  int rand1 = (int) (Math.random() * colorsLength);
  int rand2 = (int) (Math.random() * colorsLength);

  while(rand1==rand2){
      //int rand2 = (int) (Math.random() * colorsLength); - wrong
      //rand2 is already defined, you can write only
      rand2 = (int) (Math.random() * colorsLength);
  }

另外，如果你想要2个不同的随机数，你可以：

  int rand1 = (int) (Math.random() * colorsLength);
  int rand2 = (int) (Math.random() * (colorsLength-1));
  if(rand2 >= rand1) rand2++;

Answer 5

好的。你在这里写的东西有很多问题。我会尽力帮助你解决其中一些问题。

首先，正如bas指出的那样，一般来说，如果你想比较两个值以查看它们是否相等，你可以使用==，而不是=。例如：

if ( x == y ) {
  //DO STUFF
}

其次，bas也指出了这一点，在Java中你不能使用==来比较字符串。你需要做的是：

if ( string1.equals(string2) ) {
  //DO STUFF
}

第三。 “而”。这个会给你带来很多问题。虽然意味着继续执行下面的代码，直到其测试为假。所以，当你这样做时：

while ( myString.equals( "bananas" ) ) {
  System.out.println ( "Lots of bananas." );
}

如果字符串是“香蕉”，那么你会得到这个：

Lots of bananas.
Lots of bananas.
Lots of bananas.
Lots of bananas.
Lots of bananas.
Lots of bananas.
Lots of bananas.
Lots of bananas.
....

永远。你真正想要使用的是另一个if。实际上，这里也有一个方便的逻辑。您可以修改语句以使用其他ifs，而不是一堆if，因为所有这些选项都是互斥的：

if ( string1.equals("yellow")) {
  if ( string2.equals("green")) {
    System.out.println("stuff");
  }
  else if ( string2.equals("blue")) {
    System.out.println("more stuff");
  }
}
else if ( string1.equals("green")) {
  if ( string2.equals("blue")) {
    System.out.println("lalala");
  }
  else if ( string2.equals("yellow")) {
    System.out.println("more stuff");
  }
}

还有一些更好的编写程序的方法，它涉及更少的代码重复和最终更简单的逻辑，但为了避免使你超载，这可能就足够了。