Implement String#repeat(int) which was introduced in JDK 11

We can delegate the work directly to JS as the APIs are neraly indentical. The only quirk is that we we are re-checking that the provided count is non-negative to ensure that we always throw an IllegalArgumentException. PiperOrigin-RevId: 585966573
google · Nov 28, 2023 · e2042d0 · e2042d0
1 parent 83a4aac
commit e2042d0
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Showing 7 changed files with 49 additions and 2 deletions.
diff --git a/jre/java/java/lang/String.java b/jre/java/java/lang/String.java
@@ -16,6 +16,7 @@
 
 package java.lang;
 
+import static javaemul.internal.InternalPreconditions.checkArgument;
 import static javaemul.internal.InternalPreconditions.checkCriticalStringBounds;
 import static javaemul.internal.InternalPreconditions.checkNotNull;
 import static javaemul.internal.InternalPreconditions.checkPositionIndexes;
@@ -467,6 +468,11 @@ public boolean regionMatches(int toffset, String other, int ooffset, int len) {
     return regionMatches(false, toffset, other, ooffset, len);
   }
 
+  public String repeat(int count) {
+    checkArgument(count >= 0);
+    return asNativeString().repeat(count);
+  }
+
   public String replace(char from, char to) {
     return StringUtil.replace(this, from, to, /* ignoreCase= */ false);
   }
@@ -678,6 +684,8 @@ private static class NativeString {
 
     public native int lastIndexOf(String str, int start);
 
+    public native String repeat(int count);
+
     public native String replace(NativeRegExp regex, String replace);
 
     public native String substr(int beginIndex);

diff --git a/jre/java/super-wasm-alt/java/lang/String.java b/jre/java/super-wasm-alt/java/lang/String.java
@@ -16,6 +16,7 @@
  */
 package java.lang;
 
+import static javaemul.internal.InternalPreconditions.checkArgument;
 import static javaemul.internal.InternalPreconditions.checkCriticalStringBounds;
 import static javaemul.internal.InternalPreconditions.checkNotNull;
 import static javaemul.internal.InternalPreconditions.checkPositionIndexes;
@@ -597,6 +598,11 @@ public boolean regionMatches(
         : isRegionEqual(value, offset + thisStart, string.value, string.offset + start, length);
   }
 
+  public String repeat(int count) {
+    checkArgument(count >= 0);
+    return fromJsString(toJsString().repeat(count));
+  }
+
   public String replace(char oldChar, char newChar) {
     char[] buffer = value;
     int thisOffset = offset;
@@ -1006,6 +1012,8 @@ interface NativeString {
 
     NativeString toUpperCase();
 
+    NativeString repeat(int count);
+
     NativeString toLocaleLowerCase();
 
     NativeString toLocaleUpperCase();

diff --git a/jre/java/super-wasm/java/lang/String.java b/jre/java/super-wasm/java/lang/String.java
@@ -16,6 +16,7 @@
 
 package java.lang;
 
+import static javaemul.internal.InternalPreconditions.checkArgument;
 import static javaemul.internal.InternalPreconditions.checkCriticalStringBounds;
 import static javaemul.internal.InternalPreconditions.checkNotNull;
 import static javaemul.internal.InternalPreconditions.checkPositionIndexes;
@@ -539,8 +540,13 @@ public boolean regionMatches(
     return ignoreCase ? left.equalsIgnoreCase(right) : left.equals(right);
   }
 
-  public boolean regionMatches(int toffset, String other, int ooffset, int len) {
-    return regionMatches(false, toffset, other, ooffset, len);
+  public boolean regionMatches(int toffset, String other, int offset, int len) {
+    return regionMatches(false, toffset, other, offset, len);
+  }
+
+  public String repeat(int count) {
+    checkArgument(count >= 0);
+    return new String(value.repeat(count));
   }
 
   public String replace(char from, char to) {
@@ -762,6 +768,8 @@ interface NativeString {
 
     int lastIndexOf(NativeString str, int start);
 
+    NativeString repeat(int count);
+
     NativeString replace(NativeRegExp regex, NativeString replace);
 
     NativeString toLocaleLowerCase();

diff --git a/jre/javatests/com/google/j2cl/jre/java/lang/StringTest.java b/jre/javatests/com/google/j2cl/jre/java/lang/StringTest.java
@@ -998,6 +998,26 @@ public void testRegionMatches() {
     }
   }
 
+  public void testRepeat() {
+    // Empty results
+    assertEquals("", "a".repeat(0));
+    assertEquals("", "".repeat(0));
+    assertEquals("", "".repeat(10));
+
+    // Normal cases
+    assertEquals("aaaaaaaaaa", "a".repeat(10));
+    assertEquals("abc", "abc".repeat(1));
+    assertEquals("abcabc", "abc".repeat(2));
+
+    // Invalid calls
+    try {
+      String unused = "abc".repeat(-1);
+      fail("Repeating a negative count should throw an exception.");
+    } catch (IllegalArgumentException ex) {
+      // expected.
+    }
+  }
+
   public void testReplace() {
     String axax = String.valueOf(new char[] {'a', 'x', 'a', 'x'});
     String aaaa = String.valueOf(new char[] {'a', 'a', 'a', 'a'});

diff --git a/...m/google/j2cl/readable/java/importglobaljstypes/output_wasm_imports/module.imports.js.txt b/...m/google/j2cl/readable/java/importglobaljstypes/output_wasm_imports/module.imports.js.txt
@@ -93,6 +93,7 @@ function getImports() {
    'string.indexOf$2': (/** string */ $instance, /** string */ str, /** number */ startIndex, ) => $instance.indexOf(str, startIndex, ),
    'string.lastIndexOf$1': (/** string */ $instance, /** string */ str, ) => $instance.lastIndexOf(str, ),
    'string.lastIndexOf$2': (/** string */ $instance, /** string */ str, /** number */ start, ) => $instance.lastIndexOf(str, start, ),
+   'string.repeat$1': (/** string */ $instance, /** number */ count, ) => $instance.repeat(count, ),
    'string.replace$2': (/** string */ $instance, /** !RegExp */ regex, /** string */ replace, ) => $instance.replace(regex, replace, ),
    'string.toLocaleLowerCase': (/** string */ $instance, ) => $instance.toLocaleLowerCase(),
    'string.toLocaleUpperCase': (/** string */ $instance, ) => $instance.toLocaleUpperCase(),

diff --git a/...sts/com/google/j2cl/readable/java/nativejstypes/output_wasm_imports/module.imports.js.txt b/...sts/com/google/j2cl/readable/java/nativejstypes/output_wasm_imports/module.imports.js.txt
@@ -119,6 +119,7 @@ function getImports() {
    'string.indexOf$2': (/** string */ $instance, /** string */ str, /** number */ startIndex, ) => $instance.indexOf(str, startIndex, ),
    'string.lastIndexOf$1': (/** string */ $instance, /** string */ str, ) => $instance.lastIndexOf(str, ),
    'string.lastIndexOf$2': (/** string */ $instance, /** string */ str, /** number */ start, ) => $instance.lastIndexOf(str, start, ),
+   'string.repeat$1': (/** string */ $instance, /** number */ count, ) => $instance.repeat(count, ),
    'string.replace$2': (/** string */ $instance, /** !RegExp */ regex, /** string */ replace, ) => $instance.replace(regex, replace, ),
    'string.toLocaleLowerCase': (/** string */ $instance, ) => $instance.toLocaleLowerCase(),
    'string.toLocaleUpperCase': (/** string */ $instance, ) => $instance.toLocaleUpperCase(),

diff --git a/...s/com/google/j2cl/readable/java/staticjsmembers/output_wasm_imports/module.imports.js.txt b/...s/com/google/j2cl/readable/java/staticjsmembers/output_wasm_imports/module.imports.js.txt
@@ -107,6 +107,7 @@ function getImports() {
    'string.indexOf$2': (/** string */ $instance, /** string */ str, /** number */ startIndex, ) => $instance.indexOf(str, startIndex, ),
    'string.lastIndexOf$1': (/** string */ $instance, /** string */ str, ) => $instance.lastIndexOf(str, ),
    'string.lastIndexOf$2': (/** string */ $instance, /** string */ str, /** number */ start, ) => $instance.lastIndexOf(str, start, ),
+   'string.repeat$1': (/** string */ $instance, /** number */ count, ) => $instance.repeat(count, ),
    'string.replace$2': (/** string */ $instance, /** !RegExp */ regex, /** string */ replace, ) => $instance.replace(regex, replace, ),
    'string.toLocaleLowerCase': (/** string */ $instance, ) => $instance.toLocaleLowerCase(),
    'string.toLocaleUpperCase': (/** string */ $instance, ) => $instance.toLocaleUpperCase(),