The official launcher already has Java. Yours is pointing at a ghost.

Vanilla Java Edition through Mojang’s launcher uses a runtime the launcher downloads. “Unable to locate the Java runtime” usually means that download never finished, or an installation’s Java executable field points at a deleted JDK.

Minecraft Launcher runtime context and Java launch profile screen
  1. Edit the installation → Java executable → restore the bundled runtime (empty/default).
  2. Do not install Java 8 from an ad site “because Minecraft is Java.” Modern versions need the runtime Mojang ships (Java 21 for current 1.21+).
  3. If the bundled runtime itself is missing, fix the failed runtime download first — same family of issues as failed file downloads.
  4. Third-party launchers and dedicated servers are different: they often need a system JDK. This page is about Mojang’s launcher.

Microsoft Q&A threads after OS resets describe “failed to download file” followed immediately by “unable to locate Java runtime.” That is one broken fetch, two error labels.