你能纠正我在这段代码中犯的错误吗？

Question

使用getPixel（2，3） 使setColor（java.awt.Color.Black）变为黑色，然后用show（）显示图片 提示：您必须声明并使用图片参考 变量，代码如图片p。

public static void main(String[] a) 
{ 
    new Picture(FileChooser.pickAFile(); 
} 

这是我的答案，任何人都可以告诉我，如果这是正确的，如果我需要做出任何改变？任何帮助，将不胜感激。此外，这不是一个问题，即时审查考试。所以如果你打算告诉我去做自己的事，不要麻烦回答。 :)

public static void main(String[] a) 
{ 
    Picture p = new Picture; 
    new Picture(FileChooser.pickAFile(); 
    Pixel pixRef; 
    pixRef.getPixel(2,3); 
    pixRef.setColor(java.awt.Color.Black); 
    p.show(); 
} 

Answer 1

，你就会失败考试这样。

public static void main(String[] a) 
{ 
    Picture p; // constructor is a method - but seems you instantiate it in next line 
    p =new Picture(FileChooser.pickAFile()); // assign it to p 
    Pixel pixRef = new Pixel(); //avoid nullpointerexception! but logically you should get the pixel from the picture, which displayed in next line, can remove the "new Pixel()"; 
    pixRef = p.getPixel(2,3); // Shouldn't you get pixelref from picture? 
    pixRef.setColor(java.awt.Color.Black); 
    p.show(); // I don't understand this. Where do you show this? shouldn't you put it inside a Frame or something? 
} 

Answer 2

public static void main(String[] a) 
{ 

Picture p = new Picture; //what are you trying to call here? you must try checking out how to create an object it must be "Picture p = new Picture();" , and if you have just defined a parameterised constructor in Picture class and need an object of that directly do it this was 
"Picture p = new Picture(FileChooser.pickAFile()); 

new Picture(FileChooser.pickAFile()); // must be enclosed properly 
Pixel pixRef; 
pixRef.getPixel(2,3); // must be initialized before using the instance methods "Pixel pixRef = new Pixel();" 
pixRef.setColor(java.awt.Color.Black); 
p.show(); 
}