From ee1bc18e04f02349f71a40015d281d1caeed40fc Mon Sep 17 00:00:00 2001
From: Kai Yuan <kent.yuan@Gmail.com>
Date: Sun, 10 Apr 2022 04:02:29 +0200
Subject: [PATCH] filesize in humanreadable format (#12012)

---
 .../FileSizeFormatUtil.java                   | 81 +++++++++++++++++++
 .../FileSizeFormatUtilUnitTest.java           | 40 +++++++++
 2 files changed, 121 insertions(+)
 create mode 100644 java-numbers-4/src/main/java/com/baeldung/humanreadablebytes/FileSizeFormatUtil.java
 create mode 100644 java-numbers-4/src/test/java/com/baeldung/humanreadablebytes/FileSizeFormatUtilUnitTest.java

diff --git a/java-numbers-4/src/main/java/com/baeldung/humanreadablebytes/FileSizeFormatUtil.java b/java-numbers-4/src/main/java/com/baeldung/humanreadablebytes/FileSizeFormatUtil.java
new file mode 100644
index 0000000000..941aa105aa
--- /dev/null
+++ b/java-numbers-4/src/main/java/com/baeldung/humanreadablebytes/FileSizeFormatUtil.java
@@ -0,0 +1,81 @@
+package com.baeldung.humanreadablebytes;
+
+import java.text.DecimalFormat;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
+public class FileSizeFormatUtil {
+    private static final long BYTE = 1L;
+    private static final long KB = BYTE << 10;
+    private static final long MB = KB << 10;
+    private static final long GB = MB << 10;
+    private static final long TB = GB << 10;
+    private static final long PB = TB << 10;
+    private static final long EB = PB << 10;
+    private static final DecimalFormat DEC_FORMAT = new DecimalFormat("#.##");
+
+    public static String toHumanReadable(long size) {
+        if (size < 0)
+            throw new IllegalArgumentException("Invalid file size: " + size);
+        if (size >= EB) return formatSize(size, EB, "EB");
+        if (size >= PB) return formatSize(size, PB, "PB");
+        if (size >= TB) return formatSize(size, TB, "TB");
+        if (size >= GB) return formatSize(size, GB, "GB");
+        if (size >= MB) return formatSize(size, MB, "MB");
+        if (size >= KB) return formatSize(size, KB, "KB");
+        return formatSize(size, BYTE, "Bytes");
+    }
+
+    private static String formatSize(long size, long divider, String unitName) {
+        return DEC_FORMAT.format((double) size / divider) + " " + unitName;
+    }
+
+    public static String toHumanReadableWithEnum(long size) {
+        final List<SizeUnit> units = SizeUnit.unitsInDescending();
+        if (size < 0)
+            throw new IllegalArgumentException("Invalid file size: " + size);
+        String result = null;
+        for (SizeUnit unit : units) {
+            if (size >= unit.getUnitBase()) {
+                result = formatSize(size, unit.getUnitBase(), unit.name());
+                break;
+            }
+        }
+        return result == null ? formatSize(size, SizeUnit.Bytes.getUnitBase(), SizeUnit.Bytes.name()) : result;
+    }
+
+    public static String toHumanReadableByNumOfLeadingZeros(long size) {
+        if (size < 0)
+            throw new IllegalArgumentException("Invalid file size: " + size);
+        if (size < 1024) return size + " Bytes";
+        int unitIdx = (63 - Long.numberOfLeadingZeros(size)) / 10;
+        return formatSize(size, 1L << (unitIdx * 10), " KMGTPE".charAt(unitIdx) + "B");
+    }
+
+    enum SizeUnit {
+        Bytes(1L),
+        KB(Bytes.unitBase << 10),
+        MB(KB.unitBase << 10),
+        GB(MB.unitBase << 10),
+        TB(GB.unitBase << 10),
+        PB(TB.unitBase << 10),
+        EB(PB.unitBase << 10);
+
+        private final Long unitBase;
+
+        public static List<SizeUnit> unitsInDescending() {
+            List<SizeUnit> list = Arrays.asList(values());
+            Collections.reverse(list);
+            return list;
+        }
+
+        public Long getUnitBase() {
+            return unitBase;
+        }
+
+        SizeUnit(long unitBase) {
+            this.unitBase = unitBase;
+        }
+    }
+}
diff --git a/java-numbers-4/src/test/java/com/baeldung/humanreadablebytes/FileSizeFormatUtilUnitTest.java b/java-numbers-4/src/test/java/com/baeldung/humanreadablebytes/FileSizeFormatUtilUnitTest.java
new file mode 100644
index 0000000000..4326e92e2f
--- /dev/null
+++ b/java-numbers-4/src/test/java/com/baeldung/humanreadablebytes/FileSizeFormatUtilUnitTest.java
@@ -0,0 +1,40 @@
+package com.baeldung.humanreadablebytes;
+
+import org.apache.commons.io.FileUtils;
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class FileSizeFormatUtilUnitTest {
+    private final static Map<Long, String> DATA_MAP = new HashMap<Long, String>() {{
+        put(0L, "0 Bytes");
+        put(1023L, "1023 Bytes");
+        put(1024L, "1 KB");
+        put(12_345L, "12.06 KB");
+        put(10_123_456L, "9.65 MB");
+        put(10_123_456_798L, "9.43 GB");
+        put(1_777_777_777_777_777_777L, "1.54 EB");
+    }};
+
+    @Test
+    public void givenBytes_whenCalltoHumanReadableMethod_thenGetExpectedResults() {
+        DATA_MAP.forEach((in, expected) -> Assert.assertEquals(expected, FileSizeFormatUtil.toHumanReadable(in)));
+    }
+
+    @Test
+    public void givenBytes_whenCalltoHumanReadableWithEnumMethod_thenGetExpectedResults() {
+        DATA_MAP.forEach((in, expected) -> Assert.assertEquals(expected, FileSizeFormatUtil.toHumanReadableWithEnum(in)));
+    }
+
+    @Test
+    public void givenBytes_whenCalltoHumanReadableByLeadingZeros_thenGetExpectedResults() {
+        DATA_MAP.forEach((in, expected) -> Assert.assertEquals(expected, FileSizeFormatUtil.toHumanReadableByNumOfLeadingZeros(in)));
+    }
+
+    @Test
+    public void givenBytes_whenCalltoHumanReadableByFileUtils_thenOutputExpectedResults() {
+        DATA_MAP.forEach((in, expected) -> System.out.println(in + " bytes -> " + FileUtils.byteCountToDisplaySize(in)));
+    }
+}