Java Learning 22nd Day--io Comprehensive exercises Collection 3

the Long data and its native array are converted to each other/* * The Long data and its native array are converted to each other */public class Demo {
public static void Main (string[] args) {Long n = long.max_value; SYSTEM.OUT.PRINTLN (n);
byte[] buf = Long2bytes (n); Long res = Bytes2long (BUF); System.out.println (RES);
for (byte b:buf) {//System.out.println (b);//127//}
}
Byte[]--> long: High in the former public static long Bytes2long (byte[] buf) {Long l0 = (buf[0] & 0xFFL) << long L1 = (Buf[1] & 0xFFL) << 48; Long L2 = (buf[2] & 0xFFL) << 40; Long L3 = (Buf[3] & 0xFFL) << 32; Long L4 = (Buf[4] & 0xFFL) << 24; Long L5 = (Buf[5] & 0xFFL) << 16; Long L6 = (buf[6] & 0xFFL) << 8; Long L7 = (buf[7] & 0xFFL) << 0;
return l0 + L1 + L2 + L3 + L4 + l5 + L6 + L7; }
Long--> byte[]: High level in front public static byte[] Long2bytes (long N) {byte[] buf = new byte[8]; buf[0] = (byte) (n >> 56 ); BUF[1] = (byte) (n >> 48); BUF[2] = (byte) (n >> 40); BUF[3] = (byte) (n >> 32); BUF[4] = (byte) (n >> 24); BUF[5] = (byte) (n >> 16); BUF[6] = (byte) (n >> 8); BUF[7] = (byte) (n >> 0);//127
return buf; }
}
Random Access file: RandomaccessfileInstances of this class support the behavior of reading and writing random access files to random access files similar to a large byte array stored in the file system, there is a cursor or index pointing to the suppressed array. called a file pointer; The input operation reads bytes from the file pointer and moves the file pointer forward as the byte is read. Construct method: Randomaccessfile (file file, string mode) Randomaccessfile (string name, string mode) Read-write method: can read and write a variety of common types of data special methods: void SE EK (Long POS)
random access to files (simple understanding only)
ImportJava.io.RandomAccessFile; * * Randomaccessfile (File file,string mode) * Randomaccessfile (String name,string mode) * * Public classRandomaccessfiledemo { Public Static voidMain (string[] args) throwsException {Randomaccessfile RAF = NewRandomaccessfile ("Raf.txt", "RW");       RAF. Writeint (200); Move the file pointer to the file header RAF. Seek (0); inti = RAF. ReadInt (); System. out. println (i);    RAF. Close (); } }
ImportJava.io.RandomAccessFile;  * * Random Access file parent class is Object.  * Can read and write two operations.  * Specify the mode of the file operation in the constructor: * General use: "RW", which means that both can read and write. * Randomaccessfile (File file,string mode) * Randomaccessfile (String name,string mode) * * Public classRandomAccessFileDemo2 { Public Static voidMain (string[] args) throwsException {//create object Randomaccessfile RAF = NewRandomaccessfile ("Raf.txt", "RW");       Write Data RAF. Write (97); System. out. println (RAF. Getfilepointer ());       RAF. Writeint (200); System. out. println (RAF. Getfilepointer ());       RAF. writeUTF ("Hello"); System. out. println (RAF. Getfilepointer ());       RAF. writeUTF ("World"); System. out. println (RAF. Getfilepointer ()); Navigate to the string offset//Raf.seek (12); //Read a string that reads the method to match the true data type that will be read//String s = Raf.readutf ();             System.out.println (s); Read the specified string multiple times for( inti = 0; I <5;          i + +) {RAF. Seek (12); System. out. println (RAF. readUTF ());    //Release Resource RAF. Close (); } }


there is a string in the random Access file, how do I read the string multiple times?

Properties classis not part of the IO package, but because some operations and IO flow related, so put it here in Io, as a subclass of MAP use: Mainly add elements and traversal-specific methods: setProperty//Set configuration content GetProperty//Get configuration content Stringpropertynames