String Parsing: indexOf & substring

Extract pieces from a string using index positions — step through real examples to see exactly which characters get selected

Choose a Scenario

Found by indexOf

First extraction

Second extraction

Third extraction

Exclusive end (not included)

Step 0 / 0

Try It Yourself

Enter a string and a delimiter to see how indexOf() and substring() would split it.

Shortcut: split()

When you just need all the pieces, split() does it in one call:

Tip: Use indexOf() + substring() when you need precise control over which part you extract. Use split() when you want all pieces at once.

Key Concepts

indexOf(String target)

Returns the index of the first occurrence of target

Returns -1 if not found

lastIndexOf(String target)

Returns the index of the last occurrence of target

Useful when delimiter appears more than once

substring(int start)

Returns chars from start to the end of the string

One argument = "from here to the end"

substring(int start, int end)

Returns chars from start up to but NOT including end

The end index is EXCLUSIVE — this is the #1 source of confusion!

Common Mistake: Thinking substring(0, 4) includes index 4. It does NOT. It returns characters at indices 0, 1, 2, 3 only.

The Pattern

          // Find the delimiter

          int pos = str.indexOf("-");

          // Get left part

          String left = str.substring(0, pos);

          // Get right part

          String right = str.substring(pos + 1);

Why pos + 1? Because pos is the index of the delimiter itself. We want to start after it, so we add 1.