---
name: java8-utf8-compile
description: >-
  Compile or rebuild this Java 8 MES client with UTF-8 encoding and JDK 8 only.
  Use whenever compiling Java, running javac, fixing class file version errors
  (55.0 vs 52.0), or building mesclient-qmOP180A / similar Java 8 projects.
---

# Java 8 + UTF-8 编译

## When to use

- 任何 `javac` / Rebuild / 编译失败
- 报错：`类文件具有错误的版本 55.0, 应为 52.0`

## Rules

1. Always pass `-encoding UTF-8`
2. Always target Java 8: `-source 1.8 -target 1.8` (class major **52**)
3. Never leave Java 11+ class files (major **55**) in `bin/`

## Compiler

Prefer:

```text
D:\java\jdk-8u202\bin\javac.exe
```

Fallback: `D:\java\jdk-8\bin\javac.exe`

## Example

```powershell
$javac8 = "D:\java\jdk-8u202\bin\javac.exe"
$src = "src"
$out = "bin"
$lib = "lib"
$cp = ((Get-ChildItem "$lib\*.jar").FullName -join ";") + ";$out"
& $javac8 -encoding UTF-8 -source 1.8 -target 1.8 -cp $cp -d $out @(Get-ChildItem "$src\com\mes\plc\*.java").FullName
```

## Recovery

Delete bad classes under `bin/com/mes/...` then recompile with JDK 8 as above.