Determine if an Integer's Square Root Is an Integer in Java Article by Abdallah Sawan

java-numbers-4/src/main/java/com/baeldung/perfectsquare/PerfectSquareUtil.java

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+package com.baeldung.perfectsquare;
+
+public class PerfectSquareUtil {
+
+    public static boolean isPerfectSquareByUsingSqrt(long n) {
+        if (n <= 0)
+            return false;
+        double perfectSquare = Math.sqrt(n);
+        long tst = (long)(perfectSquare + 0.5);
+        return tst*tst == n;
+    }
+
+    public static boolean isPerfectSquareByUsingBinarySearch(long low, long high, long number) {
+        long check = (low + high) / 2L;
+        if (high < low)
+            return false;
+        if (number == check * check) {
+            return true;
+        } else if (number < check * check) {
+            high = check - 1L;
+            return isPerfectSquareByUsingBinarySearch(low, high, number);
+        } else {
+            low = check + 1L;
+            return isPerfectSquareByUsingBinarySearch(low, high, number);
+        }
+    }
+
+    public static boolean isPerfectSquareByUsingNewtonMethod(long n) {
+        long x1 = n;
+        long x2 = 1L;
+        while (x1 > x2) {
+            x1 = (x1 + x2) / 2L;
+            x2 = n / x1;
+        }
+        return x1 == x2 && n % x1 == 0L;
+    }
+
+    public static boolean isSquareNumberWithOptimization(long n) {
+        if (n < 0)
+            return false;
+        switch ((int) (n & 0xF)) {
+            case 0: case 1: case 4: case 9:
+                long tst = (long) Math.sqrt(n);
+                return tst * tst == n;
+            default:
+                return false;
+        }
+    }
+}

java-numbers-4/src/test/java/com/baeldung/perfectsquare/PerfectSquareUnitTest.java

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+package com.baeldung.perfectsquare;
+
+import org.junit.Test;
+import static org.junit.Assert.assertEquals;
+
+public class PerfectSquareUnitTest {
+
+    @Test
+    public void test0xFFAssignedToInteger() {
+        long n = 18676209273604L; //‬ 18676209273604 = 43621598 * 43621598
+        boolean expectedValue = true;
+        assertEquals(expectedValue, PerfectSquareUtil.isPerfectSquareByUsingSqrt(n));
+        assertEquals(expectedValue, PerfectSquareUtil.isPerfectSquareByUsingBinarySearch(1, Integer.MAX_VALUE, n));
+        assertEquals(expectedValue, PerfectSquareUtil.isPerfectSquareByUsingNewtonMethod(n));
+        assertEquals(expectedValue, PerfectSquareUtil.isSquareNumberWithOptimization(n));
+    }
+
+    @Test
+    public void test0xFFAssignedToByte() {
+        long n = 549790047707L; // prime number
+        boolean expectedValue = false;
+        assertEquals(expectedValue, PerfectSquareUtil.isPerfectSquareByUsingSqrt(n));
+        assertEquals(expectedValue, PerfectSquareUtil.isPerfectSquareByUsingBinarySearch(1, Integer.MAX_VALUE, n));
+        assertEquals(expectedValue, PerfectSquareUtil.isPerfectSquareByUsingNewtonMethod(n));
+        assertEquals(expectedValue, PerfectSquareUtil.isSquareNumberWithOptimization(n));
+    }
+}