Final variable assignment with try/catch

One way to do this is by introducing a (non-final) temporary variable, but you said you didn’t want to do that.

Another way is to move both branches of the code into a function:

final int x = getValue();

private int getValue() {
  try {
    return Integer.parseInt("someinput");
  }
  catch(NumberFormatException e) {
    return 42;
  }
}

Whether or not this is practical depends on the exact use case.

All in all, as long as x is a an appropriately-scoped local variable, the most practical general approach might be to leave it non-final.

If, on the other hand, x is a member variable, my advice would be to use a non-final temporary during initialization:

public class C {
  private final int x;
  public C() {
    int x_val;
    try {
      x_val = Integer.parseInt("someinput");
    }
    catch(NumberFormatException e) {
      x_val = 42;
    }
    this.x = x_val;
  }
}