在尝试不同的方法来使用变量时出错 [英] Error when trying to use variable in different method
问题描述
在我的最后一个问题，下面的建议<一后href=\"https://stackoverflow.com/questions/35118263/using-variable-from-another-method-in-java#comment57956881_35118263\">HERE ，我遇到了与异常的问题：java.lang.ArrayIndexOutOfBoundsException
我的程序读取从大约（目前）两个粒子和它们的当前位置，速度的文件数据，和力（与一个x，y和z为所有三个属性）。这是我的文件：
2
1 1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
2 1 1.5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
第一个数字是的的计数的，有多少粒子有。每个粒子都有一个ID，类型，位置，速度和力量。
我所试图做的是用的ReadFile的局部变量（）在主，并企图修复我的previous问题。
下面是我的code：
进口的java.io.File;
进口java.io.IOException异常;
进口的java.util。*;
进口java.io.FileReader;
进口java.io.FileNotFoundException;公共类粒子{
INT particleID;
INT particleType;
双particlePosition [] =新的双[3];
双particleVelocity [] =新的双[3];
双particleForce [] =新的双[3];
静态诠释计数;
静态INT电流= 0;
静态扫描仪READDATA;公共静态无效的主要（字串[] args）{ INT K = 100; //在[N / M]或[公斤*米/秒^ 2]
INT M = 1; //在[公斤]
双X0 = 1; //在[M]。
双T; //在[S]
双DT; //在[S]
双oldForce1;
双oldForce2;
双CURTIME = 0;
双finTime; T = 1 /（（1 /（2 *（Math.PI）））*的Math.sqrt（2 * K / M））;
的System.out.println（T）; DT = T / 150; ReadFile的（）;
粒子[] mainParticles = Particle.readfile（）;
的System.out.println（第一：[+ mainParticles [0] .particlePosition [0] +，+ 0 +]）;
的System.out.println（二：[+ mainParticles [1] .particlePosition [0] +，+ 0 +]）;}公共静态粒子[] ReadFile的（）{ 粒子[] = listParticles新粒子[统计] 尝试{
READDATA =新的扫描仪（新文件（SRC / 2particle-initial.data））;
}
赶上（例外五）{
的System.out.println（找不到文件）;
} 数= readData.nextInt（）; 而（电流I计数）{
listParticles [当前] =新粒子（）;
listParticles [电流] .particleID = readData.nextInt（）;
listParticles [电流] .particleType = readData.nextInt（）; listParticles [电流] .particlePosition [0] = readData.nextDouble（）;
listParticles [电流] .particlePosition [1] = readData.nextDouble（）;
listParticles [电流] .particlePosition [2] = readData.nextDouble（）; listParticles [电流] .particleVelocity [0] = readData.nextDouble（）;
listParticles [电流] .particleVelocity [1] = readData.nextDouble（）;
listParticles [电流] .particleVelocity [2] = readData.nextDouble（）; listParticles [电流] .particleForce [0] = readData.nextDouble（）;
listParticles [电流] .particleForce [1] = readData.nextDouble（）;
listParticles [电流] .particleForce [2] = readData.nextDouble（）; 当前++;
}
电流= 0; 的System.out.println（第一：[+ listParticles [0] .particlePosition [0] +，+ 0 +]）;
的System.out.println（二：[+ listParticles [1] .particlePosition [0] +，+ 0 +]）; readData.close（）;
返回listParticles;
}
}
在你的 ReadFile的（）方法，你想创建一个大小的数组计数在计数已经从文件中读取，因此它总是创建大小为0（类型的默认值的数组 INT ）
以下部分更改
粒子[] = listParticles新粒子[统计] 尝试{
READDATA =新的扫描仪（新文件（SRC / 2particle-initial.data））;
}
赶上（例外五）{
的System.out.println（找不到文件）;
} 数= readData.nextInt（）;
到
{尝试
READDATA =新的扫描仪（新文件（SRC / 2particle-initial.data））;
}
赶上（例外五）{
的System.out.println（找不到文件）;
} 数= readData.nextInt（）; 粒子[] = listParticles新粒子[统计]
在第2 code块变量计数设置创建阵列之前，所以它创造适当大小的阵列
After following the advice on my last question HERE , I ran into the problem with an exception: java.lang.ArrayIndexOutOfBoundsException
My program reads data from a file about (currently) two particles and their current position, velocity, and force (with an x,y, and z for all three attributes). Here is my file:
2
1 1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
2 1 1.5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
The first number is count, how many particles there are. Each particle has an ID, type, and position, velocity, and force.
What I am trying to do is to use the local variable of readfile() in main, and attempted to fix my previous problem.
Here is my code:
import java.io.File;
import java.io.IOException;
import java.util.*;
import java.io.FileReader;
import java.io.FileNotFoundException;
public class Particle {
int particleID;
int particleType;
double particlePosition[] = new double[3];
double particleVelocity[] = new double[3];
double particleForce[] = new double[3];
static int count;
static int current = 0;
static Scanner readData;
public static void main(String[] args) {
int k = 100; // in [N/m] or [kg*m/s^2]
int m = 1; // in [kg]
double x0 = 1; // in [m]
double t; // in [s]
double dt; // in [s]
double oldForce1;
double oldForce2;
double curTime = 0;
double finTime;
t = 1/((1/(2*(Math.PI))) * Math.sqrt(2*k/m));
System.out.println(t);
dt = t/150;
readfile();
Particle [] mainParticles = Particle.readfile();
System.out.println("First: [ " + mainParticles[0].particlePosition[0] + " , " + 0 + " ]");
System.out.println("Second: [ " + mainParticles[1].particlePosition[0] + " , " + 0 + " ]");
}
public static Particle[] readfile(){
Particle [] listParticles = new Particle[count];
try{
readData = new Scanner(new File("src/2particle-initial.data"));
}
catch(Exception e){
System.out.println("Could not find file");
}
count = readData.nextInt();
while (current < count){
listParticles[current] = new Particle();
listParticles[current].particleID = readData.nextInt();
listParticles[current].particleType = readData.nextInt();
listParticles[current].particlePosition[0] = readData.nextDouble();
listParticles[current].particlePosition[1] = readData.nextDouble();
listParticles[current].particlePosition[2] = readData.nextDouble();
listParticles[current].particleVelocity[0] = readData.nextDouble();
listParticles[current].particleVelocity[1] = readData.nextDouble();
listParticles[current].particleVelocity[2] = readData.nextDouble();
listParticles[current].particleForce[0] = readData.nextDouble();
listParticles[current].particleForce[1] = readData.nextDouble();
listParticles[current].particleForce[2] = readData.nextDouble();
current++;
}
current = 0;
System.out.println("First: [ " + listParticles[0].particlePosition[0] + " , " + 0 + " ]");
System.out.println("Second: [ " + listParticles[1].particlePosition[0] + " , " + 0 + " ]");
readData.close();
return listParticles;
}
}
In your readFile() method, you are trying to create an array of size count before count has been read from the file, so it always creates an array of size 0 (Default value of type int)
Change below part
Particle [] listParticles = new Particle[count];
try{
readData = new Scanner(new File("src/2particle-initial.data"));
}
catch(Exception e){
System.out.println("Could not find file");
}
count = readData.nextInt();
to
try{
readData = new Scanner(new File("src/2particle-initial.data"));
}
catch(Exception e){
System.out.println("Could not find file");
}
count = readData.nextInt();
Particle [] listParticles = new Particle[count];
In the 2nd code block variable count is set before creating array, and so it creates array of appropriate size
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