Unwinds Java exception stack and converts it to a formatted string.

formatException.java

/**
 * Unwinds Java exception stack and converts it to a formatted string.
 *
 * e.g.
 *
 * Exception in thread "main"
 * java.lang.RuntimeException: java.lang.RuntimeException: test
 *     at com.example.Main.foo(Main.java:50)
 *     at com.example.Main.test(Main.java:40)
 *     at com.example.Main.main(Main.java:14)
 * Caused by: java.lang.RuntimeException: java.lang.RuntimeException: test
 * java.lang.RuntimeException: test
 *     at com.example.Main.bar(Main.java:55)
 *     at com.example.Main.foo(Main.java:48)
 *     at com.example.Main.test(Main.java:40)
 *     at com.example.Main.main(Main.java:14)
 */

import java.util.ArrayList;
import java.util.Arrays;
import java.util.function.Function;
import java.util.stream.Collectors;
    
String formatException(Throwable e) {
    Function<Throwable, String> toStackTrace = e1 ->
        e1 + "\n\tat " + Arrays.stream(e1.getStackTrace())
            .map(StackTraceElement::toString)
            .collect(Collectors.joining("\n\tat ")) + "\n";

    Function<Throwable, String> unwindCause = e1 -> {
        var cause = new ArrayList<String>();
        while (e1.getCause() != null) {
            cause.add("Caused by: " + e1 + "\n" + toStackTrace.apply(e1.getCause()));
            e1 = e1.getCause();
        }
        return String.join("\n", cause) + "\n";
    };

    return "Exception in thread " +
        "\"" + Thread.currentThread().getName() + "\"\n" +
        toStackTrace.apply(e) +
        unwindCause.apply(e);
}