我無法理解返回值

Question

因此對於此程序，我必須使用一個方法，如果第一個圓圈較小，則返回-1;如果兩個圓圈的大小相同，則返回0;如果第一個圓圈返回1，則返回1更大。根據此方法的返回值，主要方法應打印一行輸出，如： 綠色圓圈小於紅色圓圈。

but i dont know how to program it to where 

    if (r1 > r2) 
     return -1; 

    so that the main method prints 

    r1 is bigger then r2 



    BEFORE CHANGES this is what i had when i asked the question 




     import java .awt.*; // for the graphics classs 
     import java .util.*;// for scanner class 
     public class Circles{ 
     public static void main(String[] args){ 
     Scanner input = new Scanner(System.in); //scanner object 
     DrawingPanel panel=new DrawingPanel(400,300); 
     Graphics gObject = panel.getGraphics(); //grahics object 
     // get info on circles 
     System.out.println("please enter your coordnates for the blue circle"); 
     int x1=input.nextInt(); 
     int y1=input.nextInt(); 
     System.out.println("please enter your radius for the blue circle"); 
     int r1=input.nextInt(); 
     System.out.println("please enter your coordnates for the red circle"); 
     int x2=input.nextInt(); 
     int y2=input.nextInt(); 
     System.out.println("please enter your radius for the red circle"); 
     int r2=input.nextInt(); 
     System.out.println("please enter your coordnates for the pink circle"); 
     int x3=input.nextInt(); 
     int y3=input.nextInt(); 
     System.out.println("please enter your radius for the pink circle"); 
     int r3=input.nextInt(); 
     gObject.setColor(Color.BLUE); 
     drawCircle(gObject,x1 ,y1 ,r1); 
     gObject.setColor(Color.RED); 
     drawCircle(gObject,x2,y2,r2); 
     gObject.setColor(Color.PINK); 
     drawCircle(gObject,x3,y3,r3); 
     compare(r1,r2); 
     compare(r1,r3); 
     compare(r2,r3); 

     }//end of main 

     public static void drawCircle(Graphics g, int x1 , int y1 , int r1){ 
     int X1 = (x1-r1); 
     int Y1 = (y1 - r1); 

     g.fillOval(X1 , Y1 , 2*r1 , 2*r1); 
     }//end of drawcircle 
     //start of compare 
     public static void compare(int r1 , int r2){ 
     if (r1<r2){ 
     System.out.println("Second circle is bigger then The First"); 

     } 
     else if (r1 == r2){ 
      System.out.println("the circles are the same"); 

     } 
      else if (r1 > r2){ 
      System.out.println("Second is smaller then First"); 

      } 

     }} 

下面是修改的，對於在錯誤的某些原因增多

  import java .awt.*; // for the graphics classs 
     import java .util.*;// for scanner class 
     public class Circles{ 
     public static void main(String[] args){ 
     Scanner input = new Scanner(System.in); //scanner object 
     DrawingPanel panel=new DrawingPanel(400,300); 
     Graphics gObject = panel.getGraphics(); //grahics object 
      // get info on circles 
     System.out.println("please enter your coordnates for the blue circle"); 
     int x1=input.nextInt(); 
     int y1=input.nextInt(); 
     System.out.println("please enter your radius for the blue circle"); 
     int r1=input.nextInt(); 
     System.out.println("please enter your coordnates for the red circle"); 
     int x2=input.nextInt(); 
     int y2=input.nextInt(); 
     System.out.println("please enter your radius for the red circle"); 
     int r2=input.nextInt(); 
     System.out.println("please enter your coordnates for the pink circle"); 
     int x3=input.nextInt(); 
     int y3=input.nextInt(); 
     System.out.println("please enter your radius for the pink circle"); 
     int r3=input.nextInt(); 
      gObject.setColor(Color.BLUE); 
      drawCircle(gObject,x1 ,y1 ,r1); 
      gObject.setColor(Color.RED); 
     drawCircle(gObject,x2,y2,r2); 
     gObject.setColor(Color.PINK); 
     drawCircle(gObject,x3,y3,r3); 
     compare(r1,r2); 
      compare(r1,r3); 
     compare(r2,r3); 
     int cmpResult = compare(r1, r2); 
      if (cmpResult == -1) { 
     System.out.println("r1 is smaller then r2"); 
     } else if (cmpResult == 0) { 
     System.out.println("r1 and r2 are the same"); 
      } else { 
      System.out.println("r1 is bigger then r2"); 
     } 
      System.out.println("Second circle is bigger then The First"); 
      }//end of main 

     public static void drawCircle(Graphics g, int x1 , int y1 , int r1){ 
      int X1 = (x1-r1); 
     int Y1 = (y1 - r1); 

      g.fillOval(X1 , Y1 , 2*r1 , 2*r1); 
      }//end of drawcircle 
      //start of compare 
      public static int compare(int r1 , int r2, cmpResult){ 
     if (r1<r2){ 
     return -1; 

      } 
      else if (r1 == r2){ 
      return 0; 

     } 
      else if (r1 > r2){ 
      return 1; 

      } 

      } } 

繼承人的錯誤，它給我

 3 errors found: 
    File: J:\CS Projects\Circles.java [line: 49] 
    Error: Syntax error, insert "}" to complete ClassBody 
    File: J:\CS Projects\Circles.java [line: 51] 
    Error: Syntax error on token "cmpResult", VariableDeclaratorId expected after this token 
    File: J:\CS Projects\Circles.java [line: 65] 
    Error: Syntax error on token "}", delete this token 

希望那清楚......如果你們需要我發佈代碼我目前爲止我會

Answer 1

您的假設compareTo方法「enco德」與（不那麼）特殊代碼的比較結果：

• 在第一圈是小，它需要返回-1，
• 當圈都是一樣的，它需要返回0
• 當第一個圓圈更大時，它需要返回1。

這意味着主要方法應該做同樣的解碼：

• 當它看到-1，就必須當它看到0打印「小」，
• ，它必須打印「相同「，而
• 當它看到1時，它必須打印」更大「。 then - -

所有這一切都可以用的if一個順序進行else聲明：

int cmpResult = compareTo(r1, r2); 
if (cmpResult == -1) { 
    System.out.println("r1 is smaller then r2"); 
} else if (cmpResult == 0) { 
    System.out.println("r1 and r2 are the same"); 
} else { 
    System.out.println("r1 is bigger then r2"); 
} 

Answer 2

如果a=5; b=6。 a>b回報boolean值，以便你可以這樣寫：

int compare_radius(int a, int b) 
    { 
     return (a > b ? 1 : (a < b ? -1 : 0)); 
    } 

(condition)? val1 : val2被稱爲ternary操作。如果條件是true它返回val1否則val2。在如果a > b返回1否則你的情況下，它會檢查a < b，如果這是真的，然後返回-1否則將返回0爲a == b