java - 多个 "cannot find symbol"错误

Question

我正在解决一个中间 Java 类的家庭作业问题，但我找不到错误的根源。我收到 50 多个关于宽度、高度、网格和种子的“找不到符号”错误。之前的构造函数存在问题(我在 if 语句中声明了变量)，我认为这可能就是问题所在，但我已经修补并用 Google 搜索过，但无法确定问题所在。 (我正在终端中工作，而不是 IDE。)

//single particle diffusion
import java.util.Random;
import java.io.PrintStream;

/*****************************/
/*****************************/
/* Start Public Class NFrostN /
/*****************************/
/*****************************/

public class NFrostN {

/*****************************/
/*****************************/
/*********Constructor*********/
/*****************************/
/*****************************/
public NFrostN(String[] args){
int width;
int height;
int density;
int seed;
if (args.length > 0){
      //makes sure no more than 4 have been entered
    if (!this.checkArgs(args))
        {
        System.err.print("There's a problem with the arguments. Make sure you haven't entered a string or more than four arguments.");      
        System.exit(1);} //exit with non-0 status
this.setWidth(args);
this.setHeight(args);
this.setDensity(args);
this.setSeed(args);
                }   
int[][] grid = new int[this.width][this.height];
}   


public NFrostN(){
int width;
int height;
int density;
int seed;
this.setWidth();
this.setHeight();
this.setDensity();
this.setSeed();
int[][] grid = new int[this.width][this.height];
}




/*****************************/
/*****************************/
/***Create a Random Integer***/
/******Regular+overloaded*****/
/*****************************/

int createRandomInt(int seed,int size){
        int randomb = (int) this.randoma.nextInt(size);
        return randomb;
        }

int createRandomInt(){
        int randomb = (int) randoma.nextInt();
//      int randomc = (int) randomb.nextInt(randomb);
        return randomb;
        } 

/*****************************/
/*****************************/
/**Verify arguments and Set***/
/*****************************/
/*****************************/

private boolean checkArgs(String[] args) {
    if(args.length > 4) //if too many arguments entered. not specified, made the call
    {return false;}
    else return true;
}
/*****************************/
/*****************************/
/**Width Setter+ Overloaded***/
/*****************************/
/*****************************/

void setWidth(String args[]){
    int tempWidth;  
    if (args.length > 0){   
    int tempWidth = Integer.parseInt(args[0]);  
    if(tempWidth % 1 == 0 || tempWidth > 0)
                {   
            this.width = tempWidth;
                }
            //error message??
               }
    else
    width = 256;
            }

void setWidth(){width = 256;}


/*****************************/
/*****************************/
/**Height Setter+ Overloaded**/
/*****************************/
/*****************************/

void setHeight(String args[]){
    if (args.length > 1 ){  
        int tempHeight = Integer.parseInt(args[1]);
            if(tempHeight % 1 == 0 || tempHeight > 0)
                {   
            height = tempHeight;
                }
             //error message??
               }
    else height = 256;
}

void setHeight(){height = 256;}


/*****************************/
/*****************************/
/*Density Setter+ Overloaded**/
/*****************************/
/*****************************/

void setDensity(String args[]){
    if (args.length > 2){   
    int tempDensity = Integer.parseInt(args[2]);
        if(tempDensity % 1 == 0 || tempDensity > 0 || tempDensity <= 100)
                {   
            density = tempDensity;
                }
            //error message???
               }
    else density = 25;
}


void setDensity(){density = 25;}


/*****************************/
/*****************************/
/***Seed Setter+ Overloaded***/
/*****************************/
/*****************************/

void setSeed(String args[]){
    int tempSeed = Integer.parseInt(args[3]);
    int myRandom = (int) this.randoma.nextInt();
    if (args.length > 3){   
        if(tempSeed % 1 == 0 || tempSeed > 0 || tempSeed <= 100)
                {   
            this.seed = tempSeed;
                }
             //error message ?
               }
    else seed = myRandom;
}


Random makeRand(){
Random randoma = new Random(seed);
return randoma;
}

void setSeed(){
    Random newRand = makeRand;
    int myRandom = (int) newRand.nextInt();
    seed = myRandom;
}

/*****************************/
/*****************************/
/**********Getters************/
/*****************************/
/*****************************/

int getWidth(){return width;}
int getHeight(){return height;}
int getDensity(){return density;}
int getSeed(){return seed;}
int[][] getGrid(){return grid;}



/*****************************/
/*****************************/
/*****Sum of all in array*****/
int gridSum(){
int count = 0;
for (int i = 0; i < height; i++)
    for (int j = 0; i < width; i++){    
    {count += grid[height][width];}
        }
return count;
}




/*****************************/
/*****************************/
/*******Difusion Method*******/
/*****************************/
/*****************************/


boolean diffuse(){
    boolean filled = false;
    int diffusionSteps = ((this.height * this.width) * 2); //two times the size of the grid
    int steps = 0; //steps counter
    Random genRandom = new Random(seed);
    int indexA = (int) genRandom.nextInt(width);  //indexes within domain and range of grid
    int indexB = (int) genRandom.nextInt(height);

    while (steps <= diffusionSteps){
        NFrostN r = new NFrostN();
        //      int indexA = (int) r.createRandomInt(seed,size);
        //      int indexB = (int) r.createRandomInt(indexA,size);
                    if (grid[indexA][indexB] == 0) { //if empty
                        if (grid[indexA-1][indexB] != 0 || grid[indexA][indexB-1] != 0 || grid[indexA+1][indexB] != 0 || grid[indexA][indexB+1] != 0) //if sticks next to a particle...
                        {grid[indexA][indexB] = 1;
                            return true;
                        }
                    else {
                            steps += 1; //increase counter before moving and looping again
                            Random genRandomnew = new Random(seed);
                            int ofFour = genRandomnew.nextInt(4);
                            switch(ofFour)
                                {
                            case 1:
                                indexA++;
                                return true;


                            case 2:
                                indexB++;
                                return true;

                            case 3:
                                indexB++;
                                return true;

                            case 4:
                                indexA++;
                                return true;

                                 }
                        }
    }

}
}

/*****************************/
/*****************************/
/********Display Method*******/
/*****************************/
/*****************************/

private void display(){
PrintStream ps = new PrintStream(OutputStream);
System.out.println("P6"); //magic number
System.out.println(width); //which is which??
System.out.println(height); //which is which??
System.out.println(110); //max value
for (int i = 0; i < width; i++){  
    for (int k = 0; k < this.height; k++){
        if (this.grid[this.width][this.height] == 1){       
            byte[] rgb = {110,110,110};
            ps.write(rgb);
                        }
        else 
            {byte[] rgb = {0,0,0}; 
            ps.write(rgb);
                }
        }

    }
ps.close();
}



/*****************************/
/*****************************/
/*************Main************/
/*****************************/
/*****************************/


public static void main(String[] args) {
NFrostN frost = new NFrostN(args);
int currentFull = frost.gridSum();
while ((currentFull/(frost.getHeight()*frost.getWidth()))*100 <= frost.getDensity())
    {  //while the percentage filled is smaller or equal to the density, diffuse
        if (frost.diffuse() == true)
        {
        System.exit(0);
        }
        if (frost.diffuse() == false)
        {
        System.err.print("Error in method difuse");
        System.exit(1);
            }
        frost.display();
        currentFull = frost.gridSum();
            }
    }

}

Answer 1

您应该将这些字段声明为实例变量。但您已将它们声明为 block/local 变量，因此您无法通过 this.width 访问。此外，当您在构造函数内部声明变量时，您无法在构造函数外部访问它们。

像这样

public class NFrostN {

        int width;
        int height;
        int density;
        int seed;

当您调用 this.width 编译器时，会看到没有实例/width 变量，并给出找不到符号错误