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float ff= 1.3f;(4B)
int 4B;
long 8B;
double 8B;
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int num[] = new int[3];
int[] num;
num = new int[3];
int [] num = new int[]{1,2,3};
int [][] num;
num = new int[3][4];
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num = new int[3][];
num[0] = new int[5];
num[1] = new int[3];
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int [][] num = new int[][]{{1,2}, {3,4,5}};
int [][] num = {{...}, {...}};


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class FileTest
{
 public static void main(String[] args) throws Exception
 {
  //File f=new File("1.txt");
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  //File f=new File("E:\\JavaLesson\\Lesson7\\1.txt");//ÔÚWindowsϵͳÏÂ,Óþø¶Ô ......
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