8334328: Reduce object allocation for FloatToDecimal and DoubleToDecimal

src/java.base/share/classes/jdk/internal/math/DoubleToDecimal.java

@@ -33,6 +33,8 @@
 import static java.lang.Math.multiplyHigh;
 import static jdk.internal.math.MathUtils.*;
 
+import sun.nio.cs.ISO_8859_1;
+
 /**
  * This class exposes a method to render a {@code double} as a string.
  */
@@ -130,7 +132,8 @@ public static String toString(double v) {
         int pair = LATIN1.toDecimal(str, 0, v, null);
         int type = pair & 0xFF00;
         if (type == NON_SPECIAL) {
-            return asciiBytesToString(str, pair & 0xFF);
+            int size = pair & 0xFF;
+            return new String(str, 0, size, ISO_8859_1.INSTANCE);
         }
         return special(type);
     }

src/java.base/share/classes/jdk/internal/math/FloatToDecimal.java

@@ -33,6 +33,8 @@
 import static java.lang.Math.multiplyHigh;
 import static jdk.internal.math.MathUtils.*;
 
+import sun.nio.cs.ISO_8859_1;
+
 /**
  * This class exposes a method to render a {@code float} as a string.
  */
@@ -130,7 +132,8 @@ public static String toString(float v) {
         int pair = LATIN1.toDecimal(str, 0, v);
         int type = pair & 0xFF00;
         if (type == NON_SPECIAL) {
-            return asciiBytesToString(str, pair & 0xFF);
+            int size = pair & 0xFF;
+            return new String(str, 0, size, ISO_8859_1.INSTANCE);
         }
         return special(type);
     }

src/java.base/share/classes/jdk/internal/math/ToDecimal.java

@@ -166,12 +166,6 @@ int length(byte[] str) {
         return str.length >> coder;
     }
 
-    /* Using the deprecated constructor enhances performance */
-    @SuppressWarnings("deprecation")
-    static String asciiBytesToString(byte[] str, int index) {
-        return new String(str, 0, 0, index);
-    }
-
     static String special(int type) {
         return switch (type) {
             case PLUS_ZERO  -> "0.0";