diff --git a/java/sdk.go b/java/sdk.go
index 2dbcf4a..f388358 100644
--- a/java/sdk.go
+++ b/java/sdk.go
@@ -38,14 +38,16 @@
 var apiFingerprintPathKey = android.NewOnceKey("apiFingerprintPathKey")
 
 type sdkContext interface {
-	// sdkVersion returns the sdk_version property of the current module, or an empty string if it is not set.
-	sdkVersion() string
+	// sdkVersion returns sdkSpec that corresponds to the sdk_version property of the current module
+	sdkVersion() sdkSpec
 	// systemModules returns the system_modules property of the current module, or an empty string if it is not set.
 	systemModules() string
-	// minSdkVersion returns the min_sdk_version property of the current module, or sdkVersion() if it is not set.
-	minSdkVersion() string
-	// targetSdkVersion returns the target_sdk_version property of the current module, or sdkVersion() if it is not set.
-	targetSdkVersion() string
+	// minSdkVersion returns sdkSpec that corresponds to the min_sdk_version property of the current module,
+	// or from sdk_version if it is not set.
+	minSdkVersion() sdkSpec
+	// targetSdkVersion returns the sdkSpec that corresponds to the target_sdk_version property of the current module,
+	// or from sdk_version if it is not set.
+	targetSdkVersion() sdkSpec
 }
 
 func UseApiFingerprint(ctx android.BaseModuleContext, v string) bool {
@@ -58,79 +60,236 @@
 	return false
 }
 
-func sdkVersionOrDefault(ctx android.BaseModuleContext, v string) string {
-	var sdkVersion string
-	switch v {
-	case "", "none", "current", "test_current", "system_current", "core_current", "core_platform":
-		sdkVersion = ctx.Config().DefaultAppTargetSdk()
+// sdkKind represents a particular category of an SDK spec like public, system, test, etc.
+type sdkKind int
+
+const (
+	sdkInvalid sdkKind = iota
+	sdkNone
+	sdkCore
+	sdkCorePlatform
+	sdkPublic
+	sdkSystem
+	sdkTest
+	sdkPrivate
+)
+
+// String returns the string representation of this sdkKind
+func (k sdkKind) String() string {
+	switch k {
+	case sdkPrivate:
+		return "private"
+	case sdkNone:
+		return "none"
+	case sdkPublic:
+		return "public"
+	case sdkSystem:
+		return "system"
+	case sdkTest:
+		return "test"
+	case sdkCore:
+		return "core"
+	case sdkCorePlatform:
+		return "core_platform"
 	default:
-		sdkVersion = v
+		return "invalid"
 	}
-	if UseApiFingerprint(ctx, sdkVersion) {
-		apiFingerprint := ApiFingerprintPath(ctx)
-		sdkVersion += fmt.Sprintf(".$$(cat %s)", apiFingerprint.String())
-	}
-	return sdkVersion
 }
 
-// Returns a sdk version as a number.  For modules targeting an unreleased SDK (meaning it does not yet have a number)
-// it returns android.FutureApiLevel (10000).
-func sdkVersionToNumber(ctx android.EarlyModuleContext, v string) (int, error) {
-	switch v {
-	case "", "none", "current", "test_current", "system_current", "core_current", "core_platform":
-		return ctx.Config().DefaultAppTargetSdkInt(), nil
-	default:
-		n := android.GetNumericSdkVersion(v)
-		if i, err := strconv.Atoi(n); err != nil {
-			return -1, fmt.Errorf("invalid sdk version %q", n)
-		} else {
-			return i, nil
+// sdkVersion represents a specific version number of an SDK spec of a particular kind
+type sdkVersion int
+
+const (
+	// special version number for a not-yet-frozen SDK
+	sdkVersionCurrent sdkVersion = sdkVersion(android.FutureApiLevel)
+	// special version number to be used for SDK specs where version number doesn't
+	// make sense, e.g. "none", "", etc.
+	sdkVersionNone sdkVersion = sdkVersion(0)
+)
+
+// isCurrent checks if the sdkVersion refers to the not-yet-published version of an sdkKind
+func (v sdkVersion) isCurrent() bool {
+	return v == sdkVersionCurrent
+}
+
+// isNumbered checks if the sdkVersion refers to the published (a.k.a numbered) version of an sdkKind
+func (v sdkVersion) isNumbered() bool {
+	return !v.isCurrent() && v != sdkVersionNone
+}
+
+// String returns the string representation of this sdkVersion.
+func (v sdkVersion) String() string {
+	if v.isCurrent() {
+		return "current"
+	} else if v.isNumbered() {
+		return strconv.Itoa(int(v))
+	}
+	return "(no version)"
+}
+
+// asNumberString directly converts the numeric value of this sdk version as a string.
+// When isNumbered() is true, this method is the same as String(). However, for sdkVersionCurrent
+// and sdkVersionNone, this returns 10000 and 0 while String() returns "current" and "(no version"),
+// respectively.
+func (v sdkVersion) asNumberString() string {
+	return strconv.Itoa(int(v))
+}
+
+// sdkSpec represents the kind and the version of an SDK for a module to build against
+type sdkSpec struct {
+	kind    sdkKind
+	version sdkVersion
+	raw     string
+}
+
+// valid checks if this sdkSpec is well-formed. Note however that true doesn't mean that the
+// specified SDK actually exists.
+func (s sdkSpec) valid() bool {
+	return s.kind != sdkInvalid
+}
+
+// specified checks if this sdkSpec is well-formed and is not "".
+func (s sdkSpec) specified() bool {
+	return s.valid() && s.kind != sdkPrivate
+}
+
+// prebuiltSdkAvailableForUnbundledBuilt tells whether this sdkSpec can have a prebuilt SDK
+// that can be used for unbundled builds.
+func (s sdkSpec) prebuiltSdkAvailableForUnbundledBuild() bool {
+	// "", "none", and "core_platform" are not available for unbundled build
+	// as we don't/can't have prebuilt stub for the versions
+	return s.kind != sdkPrivate && s.kind != sdkNone && s.kind != sdkCorePlatform
+}
+
+// forPdkBuild converts this sdkSpec into another sdkSpec that is for the PDK builds.
+func (s sdkSpec) forPdkBuild(ctx android.EarlyModuleContext) sdkSpec {
+	// For PDK builds, use the latest SDK version instead of "current" or ""
+	if s.kind == sdkPrivate || s.kind == sdkPublic {
+		kind := s.kind
+		if kind == sdkPrivate {
+			// We don't have prebuilt SDK for private APIs, so use the public SDK
+			// instead. This looks odd, but that's how it has been done.
+			// TODO(b/148271073): investigate the need for this.
+			kind = sdkPublic
 		}
+		version := sdkVersion(LatestSdkVersionInt(ctx))
+		return sdkSpec{kind, version, s.raw}
 	}
+	return s
 }
 
-func sdkVersionToNumberAsString(ctx android.EarlyModuleContext, v string) (string, error) {
-	n, err := sdkVersionToNumber(ctx, v)
-	if err != nil {
-		return "", err
+// usePrebuilt determines whether prebuilt SDK should be used for this sdkSpec with the given context.
+func (s sdkSpec) usePrebuilt(ctx android.EarlyModuleContext) bool {
+	if s.version.isCurrent() {
+		// "current" can be built from source and be from prebuilt SDK
+		return ctx.Config().UnbundledBuildUsePrebuiltSdks()
+	} else if s.version.isNumbered() {
+		// sanity check
+		if s.kind != sdkPublic && s.kind != sdkSystem && s.kind != sdkTest {
+			panic(fmt.Errorf("prebuilt SDK is not not available for sdkKind=%q", s.kind))
+			return false
+		}
+		// numbered SDKs are always from prebuilt
+		return true
 	}
-	return strconv.Itoa(n), nil
+	// "", "none", "core_platform" fall here
+	return false
+}
+
+// effectiveVersion converts an sdkSpec into the concrete sdkVersion that the module
+// should use. For modules targeting an unreleased SDK (meaning it does not yet have a number)
+// it returns android.FutureApiLevel(10000).
+func (s sdkSpec) effectiveVersion(ctx android.EarlyModuleContext) (sdkVersion, error) {
+	if !s.valid() {
+		return s.version, fmt.Errorf("invalid sdk version %q", s.raw)
+	}
+	if ctx.Config().IsPdkBuild() {
+		s = s.forPdkBuild(ctx)
+	}
+	if s.version.isNumbered() {
+		return s.version, nil
+	}
+	return sdkVersion(ctx.Config().DefaultAppTargetSdkInt()), nil
+}
+
+// effectiveVersionString converts an sdkSpec into the concrete version string that the module
+// should use. For modules targeting an unreleased SDK (meaning it does not yet have a number)
+// it returns the codename (P, Q, R, etc.)
+func (s sdkSpec) effectiveVersionString(ctx android.EarlyModuleContext) (string, error) {
+	ver, err := s.effectiveVersion(ctx)
+	if err == nil && int(ver) == ctx.Config().DefaultAppTargetSdkInt() {
+		return ctx.Config().DefaultAppTargetSdk(), nil
+	}
+	return ver.String(), err
+}
+
+func sdkSpecFrom(str string) sdkSpec {
+	switch str {
+	// special cases first
+	case "":
+		return sdkSpec{sdkPrivate, sdkVersionNone, str}
+	case "none":
+		return sdkSpec{sdkNone, sdkVersionNone, str}
+	case "core_platform":
+		return sdkSpec{sdkCorePlatform, sdkVersionNone, str}
+	default:
+		// the syntax is [kind_]version
+		sep := strings.LastIndex(str, "_")
+
+		var kindString string
+		if sep == 0 {
+			return sdkSpec{sdkInvalid, sdkVersionNone, str}
+		} else if sep == -1 {
+			kindString = ""
+		} else {
+			kindString = str[0:sep]
+		}
+		versionString := str[sep+1 : len(str)]
+
+		var kind sdkKind
+		switch kindString {
+		case "":
+			kind = sdkPublic
+		case "core":
+			kind = sdkCore
+		case "system":
+			kind = sdkSystem
+		case "test":
+			kind = sdkTest
+		default:
+			return sdkSpec{sdkInvalid, sdkVersionNone, str}
+		}
+
+		var version sdkVersion
+		if versionString == "current" {
+			version = sdkVersionCurrent
+		} else if i, err := strconv.Atoi(versionString); err == nil {
+			version = sdkVersion(i)
+		} else {
+			return sdkSpec{sdkInvalid, sdkVersionNone, str}
+		}
+
+		return sdkSpec{kind, version, str}
+	}
 }
 
 func decodeSdkDep(ctx android.EarlyModuleContext, sdkContext sdkContext) sdkDep {
-	v := sdkContext.sdkVersion()
-
-	// For PDK builds, use the latest SDK version instead of "current"
-	if ctx.Config().IsPdkBuild() && (v == "" || v == "current") {
-		sdkVersions := ctx.Config().Get(sdkVersionsKey).([]int)
-		latestSdkVersion := 0
-		if len(sdkVersions) > 0 {
-			latestSdkVersion = sdkVersions[len(sdkVersions)-1]
-		}
-		v = strconv.Itoa(latestSdkVersion)
-	}
-
-	numericSdkVersion, err := sdkVersionToNumber(ctx, v)
-	if err != nil {
-		ctx.PropertyErrorf("sdk_version", "%s", err)
+	sdkVersion := sdkContext.sdkVersion()
+	if !sdkVersion.valid() {
+		ctx.PropertyErrorf("sdk_version", "invalid version %q", sdkVersion.raw)
 		return sdkDep{}
 	}
 
-	toPrebuilt := func(sdk string) sdkDep {
-		var api, v string
-		if strings.Contains(sdk, "_") {
-			t := strings.Split(sdk, "_")
-			api = t[0]
-			v = t[1]
-		} else {
-			api = "public"
-			v = sdk
-		}
-		dir := filepath.Join("prebuilts", "sdk", v, api)
+	if ctx.Config().IsPdkBuild() {
+		sdkVersion = sdkVersion.forPdkBuild(ctx)
+	}
+
+	if sdkVersion.usePrebuilt(ctx) {
+		dir := filepath.Join("prebuilts", "sdk", sdkVersion.version.String(), sdkVersion.kind.String())
 		jar := filepath.Join(dir, "android.jar")
 		// There's no aidl for other SDKs yet.
 		// TODO(77525052): Add aidl files for other SDKs too.
-		public_dir := filepath.Join("prebuilts", "sdk", v, "public")
+		public_dir := filepath.Join("prebuilts", "sdk", sdkVersion.version.String(), "public")
 		aidl := filepath.Join(public_dir, "framework.aidl")
 		jarPath := android.ExistentPathForSource(ctx, jar)
 		aidlPath := android.ExistentPathForSource(ctx, aidl)
@@ -139,17 +298,17 @@
 		if (!jarPath.Valid() || !aidlPath.Valid()) && ctx.Config().AllowMissingDependencies() {
 			return sdkDep{
 				invalidVersion: true,
-				bootclasspath:  []string{fmt.Sprintf("sdk_%s_%s_android", api, v)},
+				bootclasspath:  []string{fmt.Sprintf("sdk_%s_%s_android", sdkVersion.kind, sdkVersion.version.String())},
 			}
 		}
 
 		if !jarPath.Valid() {
-			ctx.PropertyErrorf("sdk_version", "invalid sdk version %q, %q does not exist", sdk, jar)
+			ctx.PropertyErrorf("sdk_version", "invalid sdk version %q, %q does not exist", sdkVersion.raw, jar)
 			return sdkDep{}
 		}
 
 		if !aidlPath.Valid() {
-			ctx.PropertyErrorf("sdk_version", "invalid sdk version %q, %q does not exist", sdk, aidl)
+			ctx.PropertyErrorf("sdk_version", "invalid sdk version %q, %q does not exist", sdkVersion.raw, aidl)
 			return sdkDep{}
 		}
 
@@ -173,31 +332,26 @@
 
 	// Ensures that the specificed system SDK version is one of BOARD_SYSTEMSDK_VERSIONS (for vendor apks)
 	// or PRODUCT_SYSTEMSDK_VERSIONS (for other apks or when BOARD_SYSTEMSDK_VERSIONS is not set)
-	if strings.HasPrefix(v, "system_") && numericSdkVersion != android.FutureApiLevel {
+	if sdkVersion.kind == sdkSystem && sdkVersion.version.isNumbered() {
 		allowed_versions := ctx.DeviceConfig().PlatformSystemSdkVersions()
 		if ctx.DeviceSpecific() || ctx.SocSpecific() {
 			if len(ctx.DeviceConfig().SystemSdkVersions()) > 0 {
 				allowed_versions = ctx.DeviceConfig().SystemSdkVersions()
 			}
 		}
-		if len(allowed_versions) > 0 && !android.InList(strconv.Itoa(numericSdkVersion), allowed_versions) {
+		if len(allowed_versions) > 0 && !android.InList(sdkVersion.version.String(), allowed_versions) {
 			ctx.PropertyErrorf("sdk_version", "incompatible sdk version %q. System SDK version should be one of %q",
-				v, allowed_versions)
+				sdkVersion.raw, allowed_versions)
 		}
 	}
 
-	if ctx.Config().UnbundledBuildUsePrebuiltSdks() &&
-		v != "" && v != "none" && v != "core_platform" {
-		return toPrebuilt(v)
-	}
-
-	switch v {
-	case "":
+	switch sdkVersion.kind {
+	case sdkPrivate:
 		return sdkDep{
 			useDefaultLibs:     true,
 			frameworkResModule: "framework-res",
 		}
-	case "none":
+	case sdkNone:
 		systemModules := sdkContext.systemModules()
 		if systemModules == "" {
 			ctx.PropertyErrorf("sdk_version",
@@ -214,22 +368,22 @@
 			systemModules:  systemModules,
 			bootclasspath:  []string{systemModules},
 		}
-	case "core_platform":
+	case sdkCorePlatform:
 		return sdkDep{
 			useDefaultLibs:     true,
 			frameworkResModule: "framework-res",
 			noFrameworksLibs:   true,
 		}
-	case "current":
+	case sdkPublic:
 		return toModule("android_stubs_current", "framework-res", sdkFrameworkAidlPath(ctx))
-	case "system_current":
+	case sdkSystem:
 		return toModule("android_system_stubs_current", "framework-res", sdkFrameworkAidlPath(ctx))
-	case "test_current":
+	case sdkTest:
 		return toModule("android_test_stubs_current", "framework-res", sdkFrameworkAidlPath(ctx))
-	case "core_current":
+	case sdkCore:
 		return toModule("core.current.stubs", "", nil)
 	default:
-		return toPrebuilt(v)
+		panic(fmt.Errorf("invalid sdk %q", sdkVersion.raw))
 	}
 }
 
@@ -262,6 +416,15 @@
 	ctx.Config().Once(sdkVersionsKey, func() interface{} { return sdkVersions })
 }
 
+func LatestSdkVersionInt(ctx android.EarlyModuleContext) int {
+	sdkVersions := ctx.Config().Get(sdkVersionsKey).([]int)
+	latestSdkVersion := 0
+	if len(sdkVersions) > 0 {
+		latestSdkVersion = sdkVersions[len(sdkVersions)-1]
+	}
+	return latestSdkVersion
+}
+
 func sdkSingletonFactory() android.Singleton {
 	return sdkSingleton{}
 }