Hello.
I noticed that String.concat can throw StringIndexOutOfBoundsException:
String r1 = "-".repeat(Integer.MAX_VALUE - 10);
String r2 = "ы".repeat((Integer.MAX_VALUE - 10) / 2);
System.out.println(r1.concat(r2));
On JDK 24 it gives:
Exception in thread "main" java.lang.StringIndexOutOfBoundsException:
Range [0, 0 + 2147483637) out of bounds for length 1073741807
at java.base/jdk.internal.util.Preconditions$1.apply(Preconditions.java:55)
at java.base/jdk.internal.util.Preconditions$1.apply(Preconditions.java:52)
at java.base/jdk.internal.util.Preconditions$4.apply(Preconditions.java:213)
at java.base/jdk.internal.util.Preconditions$4.apply(Preconditions.java:210)
at
java.base/jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:98)
at
java.base/jdk.internal.util.Preconditions.outOfBoundsCheckFromIndexSize(Preconditions.java:118)
at
java.base/jdk.internal.util.Preconditions.checkFromIndexSize(Preconditions.java:397)
at java.base/java.lang.String.checkBoundsOffCount(String.java:4938)
at
java.base/java.lang.StringUTF16.checkBoundsOffCount(StringUTF16.java:1789)
at java.base/java.lang.StringUTF16.inflate(StringUTF16.java:1616)
at java.base/java.lang.StringLatin1.inflate(StringLatin1.java:875)
at java.base/java.lang.String.getBytes(String.java:4812)
at
java.base/java.lang.StringConcatHelper.doConcat(StringConcatHelper.java:434)
at java.base/java.lang.String.concat(String.java:2977)
On JDK 23 it results in expected OOM:
Exception in thread "main" java.lang.OutOfMemoryError: Overflow:
String length out of range
at
java.base/java.lang.StringConcatHelper.checkOverflow(StringConcatHelper.java:66)
at java.base/java.lang.StringConcatHelper.mix(StringConcatHelper.java:125)
at
java.base/java.lang.StringConcatHelper.simpleConcat(StringConcatHelper.java:374)
at java.base/java.lang.String.concat(String.java:2990)
Andrey Turbanov
