Java读取文件为字符串方法

方法一：使用Files工具类

java.nio.file.Files工具类，不依赖三方组件
Path.of方法在jdk11才支持

    public String fileToString(String path) throws IOException {return Files.readString(Path.of(path));}

方法二：使用字符流FileReader

    public String fileToString2(String path) throws IOException {FileReader reader = new FileReader(new File(path));StringBuilder stringBuilder = new StringBuilder();char[] buffer = new char[10];int size;while ((size = reader.read(buffer)) != -1) {stringBuilder.append(buffer, 0, size);}return stringBuilder.toString();}

常见字符流和字节流

#mermaid-svg-XlFVaylvq6HmxoFr {font-family:"trebuchet ms",verdana,arial,sans-serif;font-size:16px;fill:#333;}#mermaid-svg-XlFVaylvq6HmxoFr .error-icon{fill:#552222;}#mermaid-svg-XlFVaylvq6HmxoFr .error-text{fill:#552222;stroke:#552222;}#mermaid-svg-XlFVaylvq6HmxoFr .edge-thickness-normal{stroke-width:2px;}#mermaid-svg-XlFVaylvq6HmxoFr .edge-thickness-thick{stroke-width:3.5px;}#mermaid-svg-XlFVaylvq6HmxoFr .edge-pattern-solid{stroke-dasharray:0;}#mermaid-svg-XlFVaylvq6HmxoFr .edge-pattern-dashed{stroke-dasharray:3;}#mermaid-svg-XlFVaylvq6HmxoFr .edge-pattern-dotted{stroke-dasharray:2;}#mermaid-svg-XlFVaylvq6HmxoFr .marker{fill:#333333;stroke:#333333;}#mermaid-svg-XlFVaylvq6HmxoFr .marker.cross{stroke:#333333;}#mermaid-svg-XlFVaylvq6HmxoFr svg{font-family:"trebuchet ms",verdana,arial,sans-serif;font-size:16px;}#mermaid-svg-XlFVaylvq6HmxoFr .label{font-family:"trebuchet ms",verdana,arial,sans-serif;color:#333;}#mermaid-svg-XlFVaylvq6HmxoFr .cluster-label text{fill:#333;}#mermaid-svg-XlFVaylvq6HmxoFr .cluster-label span{color:#333;}#mermaid-svg-XlFVaylvq6HmxoFr .label text,#mermaid-svg-XlFVaylvq6HmxoFr span{fill:#333;color:#333;}#mermaid-svg-XlFVaylvq6HmxoFr .node rect,#mermaid-svg-XlFVaylvq6HmxoFr .node circle,#mermaid-svg-XlFVaylvq6HmxoFr .node ellipse,#mermaid-svg-XlFVaylvq6HmxoFr .node polygon,#mermaid-svg-XlFVaylvq6HmxoFr .node path{fill:#ECECFF;stroke:#9370DB;stroke-width:1px;}#mermaid-svg-XlFVaylvq6HmxoFr .node .label{text-align:center;}#mermaid-svg-XlFVaylvq6HmxoFr .node.clickable{cursor:pointer;}#mermaid-svg-XlFVaylvq6HmxoFr .arrowheadPath{fill:#333333;}#mermaid-svg-XlFVaylvq6HmxoFr .edgePath .path{stroke:#333333;stroke-width:2.0px;}#mermaid-svg-XlFVaylvq6HmxoFr .flowchart-link{stroke:#333333;fill:none;}#mermaid-svg-XlFVaylvq6HmxoFr .edgeLabel{background-color:#e8e8e8;text-align:center;}#mermaid-svg-XlFVaylvq6HmxoFr .edgeLabel rect{opacity:0.5;background-color:#e8e8e8;fill:#e8e8e8;}#mermaid-svg-XlFVaylvq6HmxoFr .cluster rect{fill:#ffffde;stroke:#aaaa33;stroke-width:1px;}#mermaid-svg-XlFVaylvq6HmxoFr .cluster text{fill:#333;}#mermaid-svg-XlFVaylvq6HmxoFr .cluster span{color:#333;}#mermaid-svg-XlFVaylvq6HmxoFr div.mermaidTooltip{position:absolute;text-align:center;max-width:200px;padding:2px;font-family:"trebuchet ms",verdana,arial,sans-serif;font-size:12px;background:hsl(80, 100%, 96.2745098039%);border:1px solid #aaaa33;border-radius:2px;pointer-events:none;z-index:100;}#mermaid-svg-XlFVaylvq6HmxoFr :root{--mermaid-font-family:"trebuchet ms",verdana,arial,sans-serif;}

字节流

字符流

InputStream

OutputStream

FileInputStream

ByteArrayInputStream

FileOutputream

ByteArrayOutputStream

Reader

Writer

FilerReader

BufferedReader

FilerWriterer

BufferedWriter

#mermaid-svg-luUF3y1DW8D3SV4B {font-family:"trebuchet ms",verdana,arial,sans-serif;font-size:16px;fill:#333;}#mermaid-svg-luUF3y1DW8D3SV4B .error-icon{fill:#552222;}#mermaid-svg-luUF3y1DW8D3SV4B .error-text{fill:#552222;stroke:#552222;}#mermaid-svg-luUF3y1DW8D3SV4B .edge-thickness-normal{stroke-width:2px;}#mermaid-svg-luUF3y1DW8D3SV4B .edge-thickness-thick{stroke-width:3.5px;}#mermaid-svg-luUF3y1DW8D3SV4B .edge-pattern-solid{stroke-dasharray:0;}#mermaid-svg-luUF3y1DW8D3SV4B .edge-pattern-dashed{stroke-dasharray:3;}#mermaid-svg-luUF3y1DW8D3SV4B .edge-pattern-dotted{stroke-dasharray:2;}#mermaid-svg-luUF3y1DW8D3SV4B .marker{fill:#333333;stroke:#333333;}#mermaid-svg-luUF3y1DW8D3SV4B .marker.cross{stroke:#333333;}#mermaid-svg-luUF3y1DW8D3SV4B svg{font-family:"trebuchet ms",verdana,arial,sans-serif;font-size:16px;}#mermaid-svg-luUF3y1DW8D3SV4B .label{font-family:"trebuchet ms",verdana,arial,sans-serif;color:#333;}#mermaid-svg-luUF3y1DW8D3SV4B .cluster-label text{fill:#333;}#mermaid-svg-luUF3y1DW8D3SV4B .cluster-label span{color:#333;}#mermaid-svg-luUF3y1DW8D3SV4B .label text,#mermaid-svg-luUF3y1DW8D3SV4B span{fill:#333;color:#333;}#mermaid-svg-luUF3y1DW8D3SV4B .node rect,#mermaid-svg-luUF3y1DW8D3SV4B .node circle,#mermaid-svg-luUF3y1DW8D3SV4B .node ellipse,#mermaid-svg-luUF3y1DW8D3SV4B .node polygon,#mermaid-svg-luUF3y1DW8D3SV4B .node path{fill:#ECECFF;stroke:#9370DB;stroke-width:1px;}#mermaid-svg-luUF3y1DW8D3SV4B .node .label{text-align:center;}#mermaid-svg-luUF3y1DW8D3SV4B .node.clickable{cursor:pointer;}#mermaid-svg-luUF3y1DW8D3SV4B .arrowheadPath{fill:#333333;}#mermaid-svg-luUF3y1DW8D3SV4B .edgePath .path{stroke:#333333;stroke-width:2.0px;}#mermaid-svg-luUF3y1DW8D3SV4B .flowchart-link{stroke:#333333;fill:none;}#mermaid-svg-luUF3y1DW8D3SV4B .edgeLabel{background-color:#e8e8e8;text-align:center;}#mermaid-svg-luUF3y1DW8D3SV4B .edgeLabel rect{opacity:0.5;background-color:#e8e8e8;fill:#e8e8e8;}#mermaid-svg-luUF3y1DW8D3SV4B .cluster rect{fill:#ffffde;stroke:#aaaa33;stroke-width:1px;}#mermaid-svg-luUF3y1DW8D3SV4B .cluster text{fill:#333;}#mermaid-svg-luUF3y1DW8D3SV4B .cluster span{color:#333;}#mermaid-svg-luUF3y1DW8D3SV4B div.mermaidTooltip{position:absolute;text-align:center;max-width:200px;padding:2px;font-family:"trebuchet ms",verdana,arial,sans-serif;font-size:12px;background:hsl(80, 100%, 96.2745098039%);border:1px solid #aaaa33;border-radius:2px;pointer-events:none;z-index:100;}#mermaid-svg-luUF3y1DW8D3SV4B :root{--mermaid-font-family:"trebuchet ms",verdana,arial,sans-serif;}

字节流

转换

字符流

InputStream

OutputStream

InputStreamReader

OutputStreamWriter

Reader

Writer

方法三：使用Apache的Commons Io组件工具类

<dependency><groupId>commons-io</groupId><artifactId>commons-io</artifactId><version>2.11.0</version>
</dependency>

    public String fileToString(String path) throws IOException {return FileUtils.readFileToString(new File(path), StandardCharsets.UTF_8);}