由於我的if語句導致的編譯錯誤

Question

我顯然不明白我在這里做什么……我可以肯定我的錯誤僅在我包含的代碼中，但是我也有其他類。 如果我可以將其重命名為更好的標題，請告訴我，或者如果我可以包含更多信息，請告訴我。 從我在該網站上看到的信息來看，我相信你們會確切地知道編譯錯誤的含義，並且知道我做錯了什么。

這是我的代碼：

import java.io.PrintStream;
public class Shape
{
   public static void init( String args[] )
   {
      Shape[] shapes = new Shape[ 4 ];
      shapes[ 0 ] = new Circle( 22, 88, 4 );
      shapes[ 1 ] = new Square( 71, 96, 10 );
      shapes[ 2 ] = new Sphere( 8, 89, 2 );
      shapes[ 3 ] = new Cube( 79, 61, 8 );

      for ( Shape currentShape : shape );
      {
         System.out.printf( "%s: %s", 
         currentShape.getName(), currentShape );

         Object localObject;

         if ( currentShape objectof TwoDimensionalShape )
         { 
             localObject = (TwoDimensionalShape)currentShape; 

            TwoDimensionalShape twoDimensionalShape = 
               ( TwoDimensionalShape ) currentShape;

            System.out.printf( "%s's area is %s\n", 
               currentShape.getName(), twoDimensionalShape.getArea() );
         } 

         if ( currentShape objectof ThreeDimensionalShape; )
         {
            ThreeDimensionalShape threeDimensionalShape = 
               ( ThreeDimensionalShape ) currentShape;

            System.out.printf( "%s's area is %s\n", 
               currentShape.getName(), threeDimensionalShape.getArea() );
            System.out.printf( "%s's volume is %s\n",
               currentShape.getName(), 
               threeDimensionalShape.getVolume() );
         } 

         System.out.println();
      } 
   } 
} 

我的編譯錯誤：

ShapeTest.java:21: error: ')' expected
         if ( currentShape objectof TwoDimensionalShape )
                          ^
ShapeTest.java:21: error: ';' expected
         if ( currentShape objectof TwoDimensionalShape )
                                                       ^
ShapeTest.java:21: error: variable declaration not allowed here
         if ( currentShape objectof TwoDimensionalShape )
                                    ^
ShapeTest.java:33: error: ')' expected
         if (( currentShape objectof ThreeDimensionalShape; ))
                                    ^
ShapeTest.java:33: error: illegal start of expression
         if (( currentShape objectof ThreeDimensionalShape; ))
                                                          ^
ShapeTest.java:33: error: illegal start of expression
         if (( currentShape objectof ThreeDimensionalShape; ))
                                                             ^
6 errors

Answer 1

Java中沒有objectof運算符，我認為您的意思是instanceof 。 此外，其中一種情況中存在分號放錯的地方。 重寫這樣的條件：

if (currentShape instanceof TwoDimensionalShape)
if (currentShape instanceof ThreeDimensionalShape)

Answer 2

Java具有instanceof運算符，而不是objectof

在第21行中，將if (currentShape objectof TwoDimensionalShape)替換為if (currentShape objectof TwoDimensionalShape) if(currentShape instanceof TwoDimensionalShape){ //more code }

在第33行中， if (currentShape objectof ThreeDimensionalShape;)與if(currentShape instanceof ThreeDimensionalShape){ //more code }