Java has the notion of format strings, bearing a strong resemblance to format strings in other languages. It is used in JDK methods like String#format() for output conversion.
I was wondering if there's an input conversion method akin to C's scanf in Java?
Take a look at this site, it explains two methods for reading from console in java, using Scanner or the classical InputStreamReader from System.in.
Following code is taken from cited website:
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
public class ReadConsoleSystem {
public static void main(String[] args) {
System.out.println("Enter something here : ");
try{
BufferedReader bufferRead = new BufferedReader(new InputStreamReader(System.in));
String s = bufferRead.readLine();
System.out.println(s);
}
catch(IOException e)
{
e.printStackTrace();
}
}
}
--
import java.util.Scanner;
public class ReadConsoleScanner {
public static void main(String[] args) {
System.out.println("Enter something here : ");
String sWhatever;
Scanner scanIn = new Scanner(System.in);
sWhatever = scanIn.nextLine();
scanIn.close();
System.out.println(sWhatever);
}
}
Regards.
There is not a pure scanf replacement in standard Java, but you could use a java.util.Scanner for the same problems you would use scanf to solve.
Not an equivalent, but you can use a Scanner and a pattern to parse lines with three non-negative numbers separated by spaces, for example:
71 5796 2489
88 1136 5298
42 420 842
Here's the code using findAll:
new Scanner(System.in).findAll("(\\d+) (\\d+) (\\d+)")
.forEach(result -> {
int fst = Integer.parseInt(result.group(1));
int snd = Integer.parseInt(result.group(2));
int third = Integer.parseInt(result.group(3));
int sum = fst + snd + third;
System.out.printf("%d + %d + %d = %d", fst, snd, third, sum);
});
If one really wanted to they could make there own version of scanf() like so:
import java.util.ArrayList;
import java.util.Scanner;
public class Testies {
public static void main(String[] args) {
ArrayList<Integer> nums = new ArrayList<Integer>();
ArrayList<String> strings = new ArrayList<String>();
// get input
System.out.println("Give me input:");
scanf(strings, nums);
System.out.println("Ints gathered:");
// print numbers scanned in
for(Integer num : nums){
System.out.print(num + " ");
}
System.out.println("\nStrings gathered:");
// print strings scanned in
for(String str : strings){
System.out.print(str + " ");
}
System.out.println("\nData:");
for(int i=0; i<strings.size(); i++){
System.out.println(nums.get(i) + " " + strings.get(i));
}
}
// get line from system
public static void scanf(ArrayList<String> strings, ArrayList<Integer> nums){
Scanner getLine = new Scanner(System.in);
Scanner input = new Scanner(getLine.nextLine());
while(input.hasNext()){
// get integers
if(input.hasNextInt()){
nums.add(input.nextInt());
}
// get strings
else if(input.hasNext()){
strings.add(input.next());
}
}
}
// pass it a string for input
public static void scanf(String in, ArrayList<String> strings, ArrayList<Integer> nums){
Scanner input = (new Scanner(in));
while(input.hasNext()){
// get integers
if(input.hasNextInt()){
nums.add(input.nextInt());
}
// get strings
else if(input.hasNext()){
strings.add(input.next());
}
}
}
}
Obviously my methods only check for Strings and Integers, if you want different data types to be processed add the appropriate arraylists and checks for them. Also, hasNext() should probably be at the bottom of the if-else if sequence since hasNext() will return true for all of the data in the string.
Output:
Give me input:
apples 8 9 pears oranges 5
Ints gathered:
8 9 5
Strings gathered:
apples pears oranges
Data:
8 apples
9 pears
5 oranges
Probably not the best example; but, the point is that Scanner implements the Iterator class. Making it easy to iterate through the scanners input using the hasNext<datatypehere>() methods; and then storing the input.
Java always takes arguments as a string type...(String args[]) so you need to convert in your desired type.
Integer.parseInt() to convert your string into Interger.System.out.println()Example :
int a;
a = Integer.parseInt(args[0]);
and for Standard Input you can use codes like
StdIn.readInt();
StdIn.readString();
THERE'S an even simpler answer
import java.io.BufferedReader;
import java.util.Scanner;
public class Main {
public static void main(String[] args)
{
String myBeautifulScanf = new Scanner(System.in).nextLine();
System.out.println( myBeautifulScanf );
}
}
C/C++ has a notion of variable references, which makes creating something like scanf much easier. However, in Java, everything is passed by value. In the case of objects, their references are passed by value.
So, it's essentially impossible to have a concise equivalent to scanf. However, you can use java.util.Scanner, which does things similar to scanf.
So this C/C++:
int a;
float b;
scanf("%d %f", &a, &b);
is (roughly) equivalent to this Java:
int a;
float b;
try (Scanner sc = new Scanner(System.in)) {
a = sc.nextInt();
b = sc.nextFloat();
}
You can format your output in Java as described in below code snippet.
public class TestFormat {
public static void main(String[] args) {
long n = 461012;
System.out.format("%d%n", n); // --> "461012"
System.out.format("%08d%n", n); // --> "00461012"
System.out.format("%+8d%n", n); // --> " +461012"
System.out.format("%,8d%n", n); // --> " 461,012"
System.out.format("%+,8d%n%n", n); // --> "+461,012"
}
}
You can read more here.
