Java Splitting and Joining Text

Splitting breaks text into pieces, and joining rebuilds pieces into one line. Split takes a pattern, not just plain text.

Split breaks a line on commas

Each comma marks a cut. The pieces print as an array.

import java.util.Arrays;
public class Main {
  public static void main(String[] args) {
    String[] parts = "ana,ben,cid".split(",");
    System.out.println(Arrays.toString(parts));
  }
}

The dot trap

An unescaped dot matches every character, so no pieces survive. An escaped dot splits on real dots.

import java.util.Arrays;
public class Main {
  public static void main(String[] args) {
    System.out.println(Arrays.toString("a.b.c".split(".")));
    System.out.println(Arrays.toString("a.b.c".split("\\.")));
  }
}

A limit leaves the rest uncut

Limit three allows three pieces only. The last piece keeps its dots.

import java.util.Arrays;
public class Main {
  public static void main(String[] args) {
    String[] parts = "a.b.c.d.e".split("\\.", 3);
    System.out.println(Arrays.toString(parts));
  }
}

Join rebuilds one line

Join places a separator between the pieces. The pieces keep their order.

public class Main {
  public static void main(String[] args) {
    String line = String.join(", ", "Ana", "Ben", "Cid");
    System.out.println(line);
  }
}

Strip and isBlank clean and judge

Strip trims both ends, and the lengths prove it. IsBlank answers true only for a spaces-only line.

public class Main {
  public static void main(String[] args) {
    String messy = "  hello  ";
    System.out.println(messy.length());
    System.out.println(messy.strip().length());
    System.out.println("   ".isBlank());
    System.out.println(" hi ".isBlank());
  }
}

Example

public class Main {
  public static void main(String[] args) {
    String line = "ana, ben, cid";
    String[] parts = line.split(",");
    for (int i = 0; i < parts.length; i++) {
      parts[i] = parts[i].strip();
    }
    System.out.println(String.join(" | ", parts));
    System.out.println(parts.length);
  }
}

Key points

Split breaks a line on its pattern into an array of pieces.
The dot is a pattern that matches any character, so it must be escaped to mean a real dot.
A limit caps the pieces and leaves the rest uncut in the last piece.
String.join rebuilds pieces into one line with a separator.
Strip cleans spaces from both ends of a line.
IsBlank judges whether a line holds only spaces.

In this example, a comma line splits into pieces, each piece strips its stray spaces, and join rebuilds a clean line.

Note

Strip removes ends only, so inner spaces stay in place.

Try it Yourself

Edit the code, then press Run.

Running is simulated

public class Main {
  public static void main(String[] args) {
    String line = "ana, ben, cid";
    String[] parts = line.split(",");
    for (int i = 0; i < parts.length; i++) {
      parts[i] = parts[i].strip();
    }
    System.out.println(String.join(" | ", parts));
    System.out.println(parts.length);
  }
}

Exercise

Splitting a.b.c.d.e with limit 3 gives which last piece?

c.d.e c d.e e