Basic File operations-InputStream byte input stream

I directly pasted the code. Please leave me a message if you have any questions.

Package org. mark. streamRW; import java. io. file; import java. io. fileInputStream; import java. io. inputStream;/*** byte output stream: OutputStream, the maximum parent class of the byte output stream in the entire IO package * byte input stream: InputStream ** InputStream uses the subclass FileInputStream. Read */public class InStream1 {/*** @ param args */public static void main (String [] args) throws Exception {// TODO Auto-generated method stub // Step 1: use the File class to find a File file File = new File ("d:" + File. separator + "test.txt"); // Step 1: instantiate the parent class Object InputStream in = null through subclass; in = new FileInputStream (file); // perform object polymorphism, instantiate // 3. read byte [] B = new byte [1024]; in. read (B); // 4. disable in. close (); System. out. println (new String (B); // convert it to String output // Legacy problem: many spaces are left. It is not that big. It has opened 1024 space and NO content is Blank }}

Legacy issues of the previous program:

Package org. mark. streamRW; import java. io. file; import java. io. fileInputStream; import java. io. inputStream; // solves the remaining issues: public class InStream2 {/*** @ param args */public static void main (String [] args) throws Exception {// TODO Auto-generated method stub // Step 1: use the File class to find a File file File = new File ("d:" + File. separator + "test.txt"); // Step 4: instantiate the parent class Object InputStream in = null through subclass; in = new FileInputStream (file); // Input Row instantiation // 3. read byte [] B = new byte [1024]; int len = in. read (B); // read the content // 4. disable in. close (); // solve the remaining issues. Refer to the method System provided by String. err. println ("length of data read:" + len); System. out. println (new String (B, 0, len); // convert it to String output // can I open up space based on the file size? }}

Solve the Problem of opening up space based on the file size

Package org. mark. streamRW; import java. io. file; import java. io. fileInputStream; import java. io. inputStream; // solves the problem of opening up space public class InStream3 {/*** @ param args */public static void main (String [] args) based on the file size) throws Exception {// TODO Auto-generated method stub // Step 1: use the File class to find a File file File = new File ("d:" + File. separator + "test.txt"); // Step 1: instantiate the parent class Object InputStream in = null through subclass; in = new FileInputStream (file); // perform object polymorphism, instantiate // 3. read byte [] B = new byte [(int) file. length ()]; // solves the problem of opening up space int len = in according to the file size. read (B); // read the content // 4. disable in. close (); // solve the remaining issues. Refer to the method System provided by String. err. println ("length of data read:" + len); System. out. println (new String (B); // convert to String output }}

Only suitable for input that knows the file size

Package org. mark. streamRW; import java. io. file; import java. io. fileInputStream; import java. io. inputStream; // only applicable to input public class InStream4 {/*** @ param args */public static void main (String [] args) that knows the file size) throws Exception {// TODO Auto-generated method stub // Step 1: use the File class to find a File file File = new File ("d:" + File. separator + "test.txt"); // Step 1: instantiate the parent class Object InputStream in = null through subclass; in = new FileInputStream (file); // perform object polymorphism, instantiate // 3. read byte [] B = new byte [(int) file. length ()]; // solves the problem of opening up space for (int I = 0; I <B. length; I ++) {B [I] = (byte) in. read ();} // int len = in. read (B); // read the content // 4. disable in. close (); // solve the remaining issues. Refer to the method System provided by String. out. println (new String (B); // convert to String output }}

When you do not know the size of the read content, you can only read the data as-1.

Package org. mark. streamRW; import java. io. file; import java. io. fileInputStream; import java. io. inputStream; // when you do not know the size of the read content, the public class InStream5 {/*** @ param args */public static void main (String [] args) Mark can only be read with the value of-1) throws Exception {// TODO Auto-generated method stub // Step 1: use the File class to find a File file File = new File ("d:" + File. separator + "test.txt"); // Step 4: instantiate the parent class Object InputStream in = null through subclass; in = new File InputStream (file); // instantiate the object through object polymorphism. // 3. read byte [] B = new byte [1024]; // solve the problem of opening up space int len = 0 according to the file size; int temp = 0; // accept each read data while (temp = in. read ())! =-1) {// indicates that there is still content. The file has not been read. B [len] = (byte) temp; len ++;} // 4. disable in. close (); // solve the remaining issues. Refer to the method System provided by String. out. println (new String (B, 0, len); // convert to String output }}

Posting is too fast ~ Close the program ~