Question

Java String.format默默地忽略传递的额外参数，这些参数未在格式字符串中使用，但如果传递的参数较少或无效则会失败。有没有办法在传递更多参数时处理这种情况？

如果参数多于格式说明符，则忽略额外参数

https://docs.oracle.com/javase/8/docs/api/java/lang/String.html#format-java.lang.String-java.lang.Object...-

private static void doStuff(Stuff stuff, String details, Object... args) {
    if(stuff.someCondition()) {
        try {
            details = String.format("Details: " + details, args);
        } catch (Exception ex) { //No Exception thrown when args are not used by
            String arguments = Arrays.stream(args)
                    .map(Objects::toString)
                    .collect(joining(";"));
            details = String.format("Details: %s Args: %s", details, arguments);
        }
    }
    stuff.process(details);
}

private static void foo() {
    Stuff stuff = new Stuff();
    doStuff(stuff, "blah blah %s ", "blah"); // No exception, works as expected
    doStuff(stuff, "blah blah %s %s", "blah"); // Fails as expected and args are printed
    doStuff(stuff, "blah blah %s", "blah", "blah"); // Silently ignores. How to handle this case?
}

Answer 1

采用不同的方法而不计算或解析%。虽然效率不高。

public static String safeFormat(String formatStr, Object... args) {
    String result = String.format(formatStr, args);

    List<Object> objects = Arrays.asList(args);
    //https://commons.apache.org/proper/commons-lang/javadocs/api-3.7/org/apache/commons/lang3/mutable/MutableBoolean.html
    MutableBoolean isCalled = new MutableBoolean(false);
    objects.add(new Object(){
        @Override
        public String toString() {
            isCalled.setTrue();
            return "";
        }
    });
    //noinspection ResultOfMethodCallIgnored
    String.format(formatStr+" %s", objects.toArray());
    if(isCalled.isFalse()) {
        throw new IllegalArgumentException("Not all arguments used by formatter");
    }
    return result;
}

Stricter String.format不会忽略额外的参数？

1 个答案: