I've already made an article for some helpful tips, but I think there is need to discuss all fuctions too. Shortly but understandable.
String
Firstly, of course, we have to initialize our string. What string is used for?
- You want to look at your string as a line, not a mas of symbols.
- You have a long text, so you work not with the letters, but with the words
- If you have big information, you need functions, that solve questions as quickly as possible.
String line;
Or with appropriate length
String line = new String[any length];
Getting a line from console
Scanner in = new Scanner(System.in);
String line = in.nextLine();
Getting position
If you need position of any symbol, use indexOf(...)
It returns a numeric value (position) of a symbol (first if they are repeating) written in brackets.
int pos = line.indexOf('any symbol');
Remember, ' ' is for symbols, " " is for String (mas of symbols).
Cut
So when you got your position, you can cut your string.
For example, line="Hello-World" and you want to get line="Hello World", so you need a position of '-' and then cut it;
We use substring(...)
Here, in brackets (start position,end position);
So you cut from 0 position to the position of '-'.
Here, the position is 5. So newline = line.substring(0,5);
Then add "tail" of our line ("World"). newline += line.substring(6, line.length());
length() is the amount of symbols in your line. So it can be used as the end position in substring.
Equals
If we want to compare two string, we use equals(...)
It returns a boolean variable, so the result can be true or false.
Mostly used with if
if (line.equals(newline)==true)
{
System.out.println("Your lines are equal");
}
Empty
Checking for emptiness is very important in case you don't want to catch mistakes.
It returns a boolean variable, so the result can be only true or false. We use isEmpty(...)
if (line.isEmpty())
{
System.out.println("Your line is empty");
}
Matches
If you want to compare not the whole lines, but some parts (using pattern), use matches()
It returns a boolean variable, so mostly used with if
Pattern = regular expression
if (line.matches ("\\d{3}")
{
System.out.println("Your line contains 3 numbers");
}
Table with more information for regex: regular expressions
I hope, for one article it is enough written. If you want more, react on this article with likes or so on.
If you have any questions, write me anytime.
Good luck in your job!
Top comments (1)
The Apache Commons StringUtils library is a nice addition to the standard String methods.