Windows PowerShellで文字コードを一括変換（BOM付き/SJIS → UTF-8 BOMなし）

Javaファイルの文字コードが UTF-8(BOM付き)、UTF-8(BOMなし)、Shift_JIS が混在している状態になっていたので、それらをすべて UTF-8（BOMなし）に一括変換したい

Powershell

$folder = "C:\Your\Target\Directory"  # ←変換対象のパスに変更！

$extensions = @("*.java", "*.xml", "*.properties")

# UTF-8かどうか判定する関数
function IsUTF8([byte[]]$bytes) {
    try {
        [System.Text.Encoding]::UTF8.GetString($bytes) | Out-Null
        return $true
    } catch {
        return $false
    }
}

foreach ($ext in $extensions) {
    Get-ChildItem -Path $folder -Recurse -Filter $ext | ForEach-Object {
        $path = $_.FullName
        $bytes = [System.IO.File]::ReadAllBytes($path)

        $encoding = New-Object System.Text.UTF8Encoding $false  # UTF-8 (BOMなし)
        $text = ""

        if ($bytes.Length -ge 3 -and $bytes[0] -eq 0xEF -and $bytes[1] -eq 0xBB -and $bytes[2] -eq 0xBF) {
            $text = [System.Text.Encoding]::UTF8.GetString($bytes, 3, $bytes.Length - 3)
            Write-Host "[UTF-8 with BOM] → $path"
        }
        elseif (IsUTF8 $bytes) {
            $text = [System.Text.Encoding]::UTF8.GetString($bytes)
            Write-Host "[UTF-8 no BOM] → $path"
        }
        else {
            $sjis = [System.Text.Encoding]::GetEncoding("shift_jis")
            $text = $sjis.GetString($bytes)
            Write-Host "[Shift_JIS] → $path"
        }

        [System.IO.File]::WriteAllText($path, $text, $encoding)
    }
}

eclipse {
    classpath {
        plusConfigurations += [configurations.testRuntimeClasspath]

        file {
            whenMerged { classpath ->
                classpath.entries.each { entry ->
                    if (entry instanceof org.gradle.plugins.ide.eclipse.model.ProjectDependency) {
                        entry.entryAttributes.remove("without_test_code")
                    }
                }
            }
        }
    }
}