# Java Interop Reference for PTC-Lisp > **Warning:** This file is auto-generated by `mix ptc.gen_docs` from `priv/functions.exs`. > Manual edits will be overwritten. Edit `priv/functions.exs` instead. PTC-Lisp emulates a subset of Java interop for LLM compatibility. These are **not** real JVM calls — they are BEAM-native implementations that mirror the Java API surface LLMs are trained on. 30 interop entries across 12 classes. See also: [Function Reference](function-reference.md) | [PTC-Lisp Specification](ptc-lisp-specification.md) | [Namespace Coverage](conformance/index.md) ### java.lang.Boolean | Name | Kind | Signature | Description | Notes | |------|------|-----------|-------------|-------| | `Boolean/parseBoolean` | Static | `(Boolean/parseBoolean s)` | Parse "true"/"false" to boolean | Matches java.lang.Boolean.parseBoolean: nil/null and every string other than case-insensitive "true" return false; non-string, non-nil inputs raise. | ### java.lang.Double | Name | Kind | Signature | Description | Notes | |------|------|-----------|-------------|-------| | `Double/NEGATIVE_INFINITY` | Constant | `Double/NEGATIVE_INFINITY, NEGATIVE_INFINITY` | Negative infinity constant (##-Inf) | | | `Double/NaN` | Constant | `Double/NaN, NaN` | Not-a-Number constant (##NaN) | | | `Double/POSITIVE_INFINITY` | Constant | `Double/POSITIVE_INFINITY, POSITIVE_INFINITY` | Positive infinity constant (##Inf) | | | `Double/parseDouble` | Static | `(Double/parseDouble s)` | Parse string to double | Compatibility alias for `(parse-double s)`. Invalid or non-string input returns nil instead of throwing. | ### java.lang.Float | Name | Kind | Signature | Description | Notes | |------|------|-----------|-------------|-------| | `Float/parseFloat` | Static | `(Float/parseFloat s)` | Parse string to float | Compatibility alias for `(parse-double s)`; PTC-Lisp uses one floating type. Invalid or non-string input returns nil instead of throwing. | ### java.lang.Integer | Name | Kind | Signature | Description | Notes | |------|------|-----------|-------------|-------| | `Integer/parseInt` | Static | `(Integer/parseInt s)` | Parse string to integer | Compatibility alias for `(parse-long s)`. Invalid or non-string input returns nil instead of throwing. | ### java.lang.Long | Name | Kind | Signature | Description | Notes | |------|------|-----------|-------------|-------| | `Long/parseLong` | Static | `(Long/parseLong s)` | Parse string to integer | Compatibility alias for `(parse-long s)`. Invalid or non-string input returns nil instead of throwing. | ### java.lang.String | Name | Kind | Signature | Description | Notes | |------|------|-----------|-------------|-------| | `.contains` | Method | `(.contains s substr)` | Returns true if string contains substring | | | `.endsWith` | Method | `(.endsWith s suffix)` | Returns true if string ends with suffix | | | `.indexOf` | Method | `(.indexOf s substr), (.indexOf s substr from-index)` | Index of first occurrence of substring, or -1 if not found | Uses grapheme indices (not byte offsets). | | `.lastIndexOf` | Method | `(.lastIndexOf s substr)` | Index of last occurrence of substring, or -1 if not found | Uses grapheme indices (not byte offsets). | | `.length` | Method | `(.length s)` | Return the grapheme count of a string | Returns grapheme count (not byte length), matching `count` and `.indexOf` index semantics. | | `.startsWith` | Method | `(.startsWith s prefix)` | Returns true if string starts with prefix | | | `.substring` | Method | `(.substring s start), (.substring s start end)` | Extract a substring by grapheme index | Indices are grapheme-based (not byte offsets). Two-arg form returns graphemes in [start, end). Raises on out-of-range indices (matches Java's StringIndexOutOfBoundsException) — note that (.substring s -1) raises rather than silently returning the last grapheme, which matters when chaining .indexOf. | | `.toLowerCase` | Method | `(.toLowerCase s)` | Convert string to lower case | | | `.toUpperCase` | Method | `(.toUpperCase s)` | Convert string to upper case | | ### java.lang.System | Name | Kind | Signature | Description | Notes | |------|------|-----------|-------------|-------| | `System/currentTimeMillis` | Static | `(System/currentTimeMillis), (currentTimeMillis)` | Return current time in milliseconds since Unix epoch | | ### java.time.Duration | Name | Kind | Signature | Description | Notes | |------|------|-----------|-------------|-------| | `.toDays` | Method | `(.toDays duration)` | Return duration length in whole days | Partial days truncate toward zero. | | `.toMillis` | Method | `(.toMillis duration)` | Return duration length in milliseconds | Works on Duration values returned by `Duration/between`. | | `Duration/between` | Static | `(Duration/between start-instant end-instant), (java.time.Duration/between start-instant end-instant)` | Return a Duration between two DateTime instants | Requires DateTime values, such as results from `Instant/parse`; LocalDate values are intentionally rejected. | ### java.time.Instant | Name | Kind | Signature | Description | Notes | |------|------|-----------|-------------|-------| | `Instant/parse` | Static | `(Instant/parse iso-string), (java.time.Instant/parse iso-string), (parse iso-string)` | Parse an ISO-8601 instant/date-time string to a DateTime | Returns an Elixir DateTime. Accepts an offset (`Z`, `+02:00`, …); an offsetless `...T...` string is treated as UTC. `.isBefore` / `.isAfter` / `.getTime` work on the result. A bare `YYYY-MM-DD` string returns a Date instead (see `LocalDate/parse`). Also available as the bare `parse` builtin. | ### java.time.LocalDate | Name | Kind | Signature | Description | Notes | |------|------|-----------|-------------|-------| | `.minusDays` | Method | `(.minusDays local-date n)` | Subtract days from a LocalDate | `n` must be an integer. | | `.plusDays` | Method | `(.plusDays local-date n)` | Add days to a LocalDate | `n` must be an integer. | | `.toEpochDay` | Method | `(.toEpochDay local-date)` | Return LocalDate epoch-day integer | Works on LocalDate values returned by `LocalDate/parse`. | | `LocalDate/parse` | Static | `(LocalDate/parse date-string), (java.time.LocalDate/parse date-string), (parse date-string)` | Parse an ISO-8601 date string (YYYY-MM-DD) to a Date | Returns an Elixir Date for `YYYY-MM-DD`. If the string carries a time component (`...T...`) it returns a DateTime instead (see `Instant/parse`) — a divergence from Java's strict `LocalDate.parse`. Also available as the bare `parse` builtin. | ### java.time.LocalDate / java.util.Date | Name | Kind | Signature | Description | Notes | |------|------|-----------|-------------|-------| | `.isAfter` | Method | `(.isAfter a b)` | Returns true if receiver comes strictly after argument (same-type only) | Works on both LocalDate and DateTime. Mixed types raise an error. | | `.isBefore` | Method | `(.isBefore a b)` | Returns true if receiver comes strictly before argument (same-type only) | Works on both LocalDate and DateTime. Mixed types raise an error. | ### java.util.Date | Name | Kind | Signature | Description | Notes | |------|------|-----------|-------------|-------| | `.getTime` | Method | `(.getTime date)` | Return Unix timestamp in milliseconds from DateTime | | | `java.util.Date.` | Constructor | `(java.util.Date.), (java.util.Date. timestamp-or-string), (java.util.Date. datetime-or-date)` | Construct current UTC time, from a timestamp / ISO-8601 / RFC-2822 string, or pass through an existing temporal value | Returns Elixir DateTime. Accepts integer (seconds or ms auto-detected), ISO-8601 (with or without offset — offsetless is treated as UTC), RFC 2822, or an existing DateTime/NaiveDateTime/Date (Date and NaiveDateTime upgrade to UTC; DateTime returns as-is). Time alone is not accepted (no date component). |