Summary

Modify the implementation of DataInputStream.readFully(byte[] b, int off, int len) to throw NullPointerException and IndexOutOfBoundsException as described in its specification,

Problem

DataInputStream.readFully(byte[] b, int off, int len) is specified to throw a NullPointerException if b is null, and an IndexOutOfBoundsException if off is negative, len is negative, or len is greater than b.length - off. For example if b was null and len was zero, then the method would fail silently without throwing a NullPointerException. Also if b was non-null, off was negative and len was zero, then the method would fail silently without throwing an IndexOutOfBoundsException.

Solution

Use Objects.checkFromIndexSize(int,int,int) to validate the parameters.

--- a/src/java.base/share/classes/java/io/DataInputStream.java  Fri Aug 07 20:39:10 2020 +0100
+++ b/src/java.base/share/classes/java/io/DataInputStream.java  Fri Aug 07 12:58:40 2020 -0700
@@ -25,6 +25,8 @@
+import java.util.Objects;
+
/**
 * A data input stream lets an application read primitive Java data
 * types from an underlying input stream in a machine-independent
@@ -192,8 +194,7 @@
    * @see        java.io.FilterInputStream#in
    */
    public final void readFully(byte b[], int off, int len) throws IOException {
-        if (len < 0)
-            throw new IndexOutOfBoundsException();
+        Objects.checkFromIndexSize(off, len, b.length);
         int n = 0;
         while (n < len) {
             int count = in.read(b, off + n, len - n);

Specification

No specification change.