Summary of Java I/O

Console I/O

For console input, use a `Scanner` object

Example:
```
Scanner stdin = new Scanner(System.in);
```
System.in = an InputStream object predefined in java.lang
Read one line at a time
```
String inputLine = stdin.nextLine();
```

Convert input

char   c = inputLine.charAt(0);
int    i = Integer.parseInt(inputLine);
long   l = Long.parseLong(inputLine);
float  f = Float.parseFloat(inputLine);
double d = Double.parseDouble(inputLine);

Read part of a line: next, nextInt, nextDouble, etc.
Test for input: hasNext, hasNextInt, etc.

For console output, use `System.out`

System.out = a PrintStream object predefined in java.lang
Useful methods
```
print
println
```
Can use with primitive data types, Strings, and any object (override the toString method to obtain desired format)

File I/O

For file input, use a `Scanner` object

Example:

File srcFile = new File("myFile.txt");
Scanner fileIn = new Scanner(srcFile);

Throws FileNotFoundException (a checked exception)

Useful methods

hasNext, hasNextInt, etc.
next, nextInt, nextLine, etc.
close

If the file has several pieces of information on each line, read one line at a time (using nextLine), then use the split method of the String class to divide the line into tokens (individual pieces of information) based on delimiters (the characters used to separate the pieces of information):
General template for using split (where line is a single line of input):
String delims = "[delimiters]+"; String[] tokens = line.split(delims); for (int i = 0; i < tokens.length; i++) do something with the tokens

For file output, use a `PrintStream` object

Example:

File dstFile = new File("myFile.txt");
PrintStream outFile = new PrintStream(dstFile);

Options
```
new PrintStream(File file) 
new PrintStream(String fileName)
```
Note: the options above
- have no automatic line flushing
- will overwrite a file if it already exists
- throw FileNotFoundException
Useful methods
```
print
println
close
```
Can use with primitive data types, Strings, and any object (override the toString method to obtain desired format)

Summary of Java I/O

Console I/O

For console input, use a Scanner object

For console output, use System.out

File I/O

For file input, use a Scanner object

For file output, use a PrintStream object

See PlanetIO.java for an example of file and console I/O

For console input, use a `Scanner` object

For console output, use `System.out`

For file input, use a `Scanner` object

For file output, use a `PrintStream` object