To implement a file reader starting from scratch, first of all, rename the class.
To implement a file reader starting from scratch, first of all, rename the class.
To implement a file reader starting from scratch, first of all, rename the class.
Any program which does I/O needs to use the facilities of the I/O package
Any program which does I/O needs to use the facilities of the I/O package
Any program which does I/O needs to use the facilities of the I/O package
To 'cat' all the files, we'll have to loop around all the arguments. Note that for the loop bound we use the array's explicit length which is stored as part of every array or string.
To 'cat' all the files, we'll have to loop around all the arguments. Note that for the loop bound we use the array's explicit length which is stored as part of every array or string.
To 'cat' all the files, we'll have to loop around all the arguments. Note that for the loop bound we use the array's explicit length which is stored as part of every array or string.
The way to handle files in Java is to set up a File object which "wraps" each file name. A File has methods for checking its existence and the settings of its attributes.
The way to handle files in Java is to set up a File object which "wraps" each file name. A File has methods for checking its existence and the settings of its attributes.
The way to handle files in Java is to set up a File object which "wraps" each file name. A File has methods for checking its existence and the settings of its attributes.
A File object can be used as the 'seed' for a new Reader object. In general there are many sorts of Readers which are all used for reading the contents of their particular objects.
A File object can be used as the 'seed' for a new Reader object. In general there are many sorts of Readers which are all used for reading the contents of their particular objects.
A File object can be used as the 'seed' for a new Reader object. In general there are many sorts of Readers which are all used for reading the contents of their particular objects.
What we specifically need here is something that reads files. That something is a FileReader...
What we specifically need here is something that reads files. That something is a FileReader...
What we specifically need here is something that reads files. That something is a FileReader...
...and since all Readers have character-reading capabilities we can take advantage of it a very familiar way.
NB Readers treat their contents as Unicode character streams whereas the old-fashioned InputStreams from Java 1.0 treat their contents as byte streams (possibly with an ASCII interpretation).
...and since all Readers have character-reading capabilities we can take advantage of it a very familiar way.
NB Readers treat their contents as Unicode character streams whereas the old-fashioned InputStreams from Java 1.0 treat their contents as byte streams (possibly with an ASCII interpretation).
...and since all Readers have character-reading capabilities we can take advantage of it a very familiar way.
NB Readers treat their contents as Unicode character streams whereas the old-fashioned InputStreams from Java 1.0 treat their contents as byte streams (possibly with an ASCII interpretation).
Unfortunately, there are many tings that can go wrong. The simplest way to cover all eventualities is to declare that the program throws miscellaneous I/O exceptions. That covers a multitude of sins like non-existing files, problems with permissions and disk crashes.
Unfortunately, there are many tings that can go wrong. The simplest way to cover all eventualities is to declare that the program throws miscellaneous I/O exceptions. That covers a multitude of sins like non-existing files, problems with permissions and disk crashes.
Unfortunately, there are many tings that can go wrong. The simplest way to cover all eventualities is to declare that the program throws miscellaneous I/O exceptions. That covers a multitude of sins like non-existing files, problems with permissions and disk crashes.
Strictly speaking, that's fine and the code is fully functional. If there is an 'exception situation', the Java Machine will terminate the program and print an error trace on the terminal. This is not very user-friendly: on second thoughts we'd better handle the errors.
Strictly speaking, that's fine and the code is fully functional. If there is an 'exception situation', the Java Machine will terminate the program and print an error trace on the terminal. This is not very user-friendly: on second thoughts we'd better handle the errors.
Strictly speaking, that's fine and the code is fully functional. If there is an 'exception situation', the Java Machine will terminate the program and print an error trace on the terminal. This is not very user-friendly: on second thoughts we'd better handle the errors.
We do this by enclosing the statements which may generate an error (which is most of them!) in a try/catch combo. In effect we are going to try to execute those statements, but if some error condition arises, we will catch it and do something about it.
We do this by enclosing the statements which may generate an error (which is most of them!) in a try/catch combo. In effect we are going to try to execute those statements, but if some error condition arises, we will catch it and do something about it.
We do this by enclosing the statements which may generate an error (which is most of them!) in a try/catch combo. In effect we are going to try to execute those statements, but if some error condition arises, we will catch it and do something about it.
We do this by enclosing the statements which may generate an error (which is most of them!) in a try/catch combo. In effect we are going to try to execute those statements, but if some error condition arises, we will catch it and do something about it.
We do this by enclosing the statements which may generate an error (which is most of them!) in a try/catch combo. In effect we are going to try to execute those statements, but if some error condition arises, we will catch it and do something about it.
The it that we catch is actually an IOException...
The it that we catch is actually an IOException...
The it that we catch is actually an IOException...
...and we will just print out an error message and carry on
...and we will just print out an error message and carry on
...and we will just print out an error message and carry on
The finished code!
public class HelloWorld{
public static void main(String[] arg){
System.out.println("Hello World");
}
}
public class HelloWorld{
public static void main(String[] arg){
System.out.println("Hello World");
}
}
public class Cat{
public static void main(String[] arg){
System.out.println("Hello World");
}
}
public class Cat{
public static void main(String[] arg){
System.out.println("Hello World");
}
}
*public class Cat{
public static void main(String[] arg){
System.out.println("Hello World");
}
}
import java.io.*;
public class Cat{
public static void main(String[] arg){
System.out.println("Hello World");
}
}
import java.io.*;
public class Cat{
public static void main(String[] arg){
System.out.println("Hello World");
}
}
import java.io.*;
public class Cat{
public static void main(String[] arg){
System.out.println("Hello World");
}
}
import java.io.*;
public class Cat{
public static void main(String[] arg){
for(int i=0; i<arg.length; i++){
...
}
}
}
import java.io.*;
public class Cat{
public static void main(String[] arg){
for(int i=0; i<arg.length; i++){
...
}
}
}
import java.io.*;
public class Cat{
public static void main(String[] arg){
for(int i=0; i<arg.length; i++){
...
}
}
}
import java.io.*;
public class Cat{
public static void main(String[] arg){
for(int i=0; i<arg.length; i++){
File f=new File(arg[i]);
...
}
}
}
import java.io.*;
public class Cat{
public static void main(String[] arg){
for(int i=0; i<arg.length; i++){
File f=new File(arg[i]);
...
}
}
}
import java.io.*;
public class Cat{
public static void main(String[] arg){
for(int i=0; i<arg.length; i++){
File f=new File(arg[i]);
...
}
}
}
import java.io.*;
public class Cat{
public static void main(String[] arg){
for(int i=0; i<arg.length; i++){
File f=new File(arg[i]);
Reader in=new ?(f);
...
}
}
}
import java.io.*;
public class Cat{
public static void main(String[] arg){
for(int i=0; i<arg.length; i++){
File f=new File(arg[i]);
Reader in=new ?(f);
...
}
}
}
import java.io.*;
public class Cat{
public static void main(String[] arg){
for(int i=0; i<arg.length; i++){
File f=new File(arg[i]);
Reader in=new ?(f);
...
}
}
}
import java.io.*;
public class Cat{
public static void main(String[] arg){
for(int i=0; i<arg.length; i++){
File f=new File(arg[i]);
Reader in=new FileReader(f);
...
}
}
}
import java.io.*;
public class Cat{
public static void main(String[] arg){
for(int i=0; i<arg.length; i++){
File f=new File(arg[i]);
Reader in=new FileReader(f);
...
}
}
}
import java.io.*;
public class Cat{
public static void main(String[] arg){
for(int i=0; i<arg.length; i++){
File f=new File(arg[i]);
Reader in=new FileReader(f);
...
}
}
}
import java.io.*;
public class Cat{
public static void main(String[] arg){
for(int i=0; i<arg.length; i++){
File f=new File(arg[i]);
Reader in=new FileReader(f);
int c;
while((c=in.read())!=-1)
System.out.print((char)c);
}
}
}
import java.io.*;
public class Cat{
public static void main(String[] arg){
for(int i=0; i<arg.length; i++){
File f=new File(arg[i]);
Reader in=new FileReader(f);
int c;
while((c=in.read())!=-1)
System.out.print((char)c);
}
}
}
import java.io.*;
public class Cat{
public static void main(String[] arg){
for(int i=0; i<arg.length; i++){
File f=new File(arg[i]);
Reader in=new FileReader(f);
int c;
while((c=in.read())!=-1)
System.out.print((char)c);
}
}
}
import java.io.*;
public class Cat{
public static void main(String[] arg) throws IOException {
for(int i=0; i<arg.length; i++){
File f=new File(arg[i]);
Reader in=new FileReader(f);
int c;
while((c=in.read())!=-1)
System.out.print((char)c);
}
}
}
import java.io.*;
public class Cat{
public static void main(String[] arg) throws IOException {
for(int i=0; i<arg.length; i++){
File f=new File(arg[i]);
Reader in=new FileReader(f);
int c;
while((c=in.read())!=-1)
System.out.print((char)c);
}
}
}
import java.io.*;
public class Cat{
public static void main(String[] arg) throws IOException {
for(int i=0; i<arg.length; i++){
File f=new File(arg[i]);
Reader in=new FileReader(f);
int c;
while((c=in.read())!=-1)
System.out.print((char)c);
}
}
}
import java.io.*;
public class Cat{
public static void main(String[] arg) {
for(int i=0; i<arg.length; i++){
File f=new File(arg[i]);
Reader in=new FileReader(f);
int c;
while((c=in.read())!=-1)
System.out.print((char)c);
}
}
}
import java.io.*;
public class Cat{
public static void main(String[] arg) {
for(int i=0; i<arg.length; i++){
File f=new File(arg[i]);
Reader in=new FileReader(f);
int c;
while((c=in.read())!=-1)
System.out.print((char)c);
}
}
}
import java.io.*;
public class Cat{
public static void main(String[] arg) {
for(int i=0; i<arg.length; i++){
* File f=new File(arg[i]);
Reader in=new FileReader(f);
int c;
while((c=in.read())!=-1)
System.out.print((char)c);
}
}
}
import java.io.*;
public class Cat{
public static void main(String[] arg) {
for(int i=0; i<arg.length; i++){
try{
File f=new File(arg[i]);
Reader in=new FileReader(f);
int c;
while((c=in.read())!=-1)
System.out.print((char)c);
}
}
}
import java.io.*;
public class Cat{
public static void main(String[] arg) {
for(int i=0; i<arg.length; i++){
try{
File f=new File(arg[i]);
Reader in=new FileReader(f);
int c;
while((c=in.read())!=-1)
System.out.print((char)c);
}
*}
}
import java.io.*;
public class Cat{
public static void main(String[] arg) {
for(int i=0; i<arg.length; i++){
try{
File f=new File(arg[i]);
Reader in=new FileReader(f);
int c;
while((c=in.read())!=-1)
System.out.print((char)c);
}
catch(?){
...
}
}}
}
import java.io.*;
public class Cat{
public static void main(String[] arg) {
for(int i=0; i<arg.length; i++){
try{
File f=new File(arg[i]);
Reader in=new FileReader(f);
int c;
while((c=in.read())!=-1)
System.out.print((char)c);
}
catch(?){
...
}
}}
}
import java.io.*;
public class Cat{
public static void main(String[] arg) {
for(int i=0; i<arg.length; i++){
try{
File f=new File(arg[i]);
Reader in=new FileReader(f);
int c;
while((c=in.read())!=-1)
System.out.print((char)c);
}
catch(?){
...
}
}}
}
import java.io.*;
public class Cat{
public static void main(String[] arg) {
for(int i=0; i<arg.length; i++){
try{
File f=new File(arg[i]);
Reader in=new FileReader(f);
int c;
while((c=in.read())!=-1)
System.out.print((char)c);
}
catch(IOException e){
...
}
}}
}
import java.io.*;
public class Cat{
public static void main(String[] arg) {
for(int i=0; i<arg.length; i++){
try{
File f=new File(arg[i]);
Reader in=new FileReader(f);
int c;
while((c=in.read())!=-1)
System.out.print((char)c);
}
catch(IOException e){
...
}
}}
}
import java.io.*;
public class Cat{
public static void main(String[] arg) {
for(int i=0; i<arg.length; i++){
try{
File f=new File(arg[i]);
Reader in=new FileReader(f);
int c;
while((c=in.read())!=-1)
System.out.print((char)c);
}
catch(IOException e){
...
}
}}
}
import java.io.*;
public class Cat{
public static void main(String[] arg) {
for(int i=0; i<arg.length; i++){
try{
File f=new File(arg[i]);
Reader in=new FileReader(f);
int c;
while((c=in.read())!=-1)
System.out.print((char)c);
}
catch(IOException e){
System.err.println(e);
}
}}
}
import java.io.*;
public class Cat{
public static void main(String[] arg) {
for(int i=0; i<arg.length; i++){
try{
File f=new File(arg[i]);
Reader in=new FileReader(f);
int c;
while((c=in.read())!=-1)
System.out.print((char)c);
}
catch(IOException e){
System.err.println(e);
}
}}
}