Add utility methods that write to a file

Author: Techcable

src/main/java/net/techcable/srglib/format/MappingsFormat.java

@@ -1,12 +1,22 @@
 package net.techcable.srglib.format;
 
+import java.io.BufferedWriter;
 import java.io.CharArrayReader;
 import java.io.CharArrayWriter;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
 import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.OutputStreamWriter;
+import java.io.Reader;
+import java.io.Writer;
+import java.nio.file.Files;
 import java.util.Arrays;
 import java.util.Iterator;
 import java.util.List;
 
+import com.google.common.base.Charsets;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.io.CharStreams;
@@ -37,6 +47,13 @@ default Mappings parse(Readable readable) throws IOException {
         return lineProcessor.getResult();
     }
 
+    default Mappings parseFile(File file) throws IOException {
+        try (Reader in = new InputStreamReader(new FileInputStream(file), Charsets.UTF_8)) {
+            // Don't worry, parse(Readable) buffers internally
+            return parse(in);
+        }
+    }
+
     default Mappings parseLines(String... lines) {
         return parseLines(Arrays.asList(lines));
     }
@@ -55,6 +72,12 @@ default Mappings parseLines(Iterator<String> lines) {
 
     void write(Mappings mappings, Appendable output) throws IOException;
 
+    default void writeToFile(Mappings mappings, File file) throws IOException {
+        try (Writer out = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(file), Charsets.UTF_8))) {
+            write(mappings, out);
+        }
+    }
+
     default List<String> toLines(Mappings mappings) {
         CharArrayWriter result = new CharArrayWriter();
         return sneakyThrowing(() -> {