try with resource是一个语法糖，可以使用该方式关闭流的前提是对象一定要实现AutoCloseable接口，其原理还是在编译的时候JDK给我们生成了finally来关闭流

源代码

public static String createImg(String message, int width, int height) {String img = "";ClassPathResource resource = new ClassPathResource("resources/font/SourceHanSansCN-Normal.ttf");try (ByteArrayOutputStream outputStream = new ByteArrayOutputStream();InputStream fis = resource.getInputStream()){//创建画布BufferedImage bi = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);//得到它的绘制环境(这张图片的笔)Graphics2D g2 = (Graphics2D) bi.getGraphics();//设置透明背景bi = g2.getDeviceConfiguration().createCompatibleImage(width, height, Transparency.TRANSLUCENT);g2 = bi.createGraphics();Font font = java.awt.Font.createFont(java.awt.Font.TRUETYPE_FONT, fis);font = font.deriveFont(Font.PLAIN, 90);//设置字体:字体、字号、大小g2.setFont(font);//设置背景颜色g2.setColor(Color.red);int locY = g2.getFontMetrics().getHeight();drawString(g2, message, 0, locY, width - g2.getFontMetrics().charWidth(' '));// 输出png图片ImageIO.write(bi, "png", outputStream);img = Base64.encode(outputStream.toByteArray());g2.dispose();} catch (IOException | FontFormatException e) {e.printStackTrace();}return img;
}

反编译class的文件

public static String createImg(String message, int width, int height) {String img = "";ClassPathResource resource = new ClassPathResource("resources/font/SourceHanSansCN-Normal.ttf");try {ByteArrayOutputStream outputStream = new ByteArrayOutputStream();Throwable var6 = null;try {InputStream fis = resource.getInputStream();Throwable var8 = null;try {BufferedImage bi = new BufferedImage(width, height, 1);Graphics2D g2 = (Graphics2D)bi.getGraphics();bi = g2.getDeviceConfiguration().createCompatibleImage(width, height, 3);g2 = bi.createGraphics();Font font = Font.createFont(0, fis);font = font.deriveFont(0, 90.0F);g2.setFont(font);g2.setColor(Color.red);int locY = g2.getFontMetrics().getHeight();drawString(g2, message, 0, locY, width - g2.getFontMetrics().charWidth(' '));ImageIO.write(bi, "png", outputStream);img = Base64.encode(outputStream.toByteArray());g2.dispose();} catch (Throwable var36) {var8 = var36;throw var36;} finally {if (fis != null) {if (var8 != null) {try {fis.close();} catch (Throwable var35) {var8.addSuppressed(var35);}} else {fis.close();}}
}} catch (Throwable var38) {var6 = var38;throw var38;} finally {if (outputStream != null) {if (var6 != null) {try {outputStream.close();} catch (Throwable var34) {var6.addSuppressed(var34);}} else {outputStream.close();}}}} catch (FontFormatException | IOException var40) {var40.printStackTrace();}return img;
}