检查字符串是否在数组中以startwith开头

Question

String[] directions = {"UP","DOWN","RIGHT","LEFT"};
String input = "DOWN 123 test";

有没有办法检查输入字符串是否在方向上以一个值开始而不使用拆分输入值？

Answer 1

当然 - 只需遍历所有方向:

private static final String[] DIRECTIONS = {"UP","DOWN","RIGHT","LEFT"};

public static String getDirectionPrefix(String input) {
    for (String direction : DIRECTIONS) {
        if (input.startsWith(direction)) {
            return direction;
        }
    }
    return null;
}

或者使用Java 8的流:

private static final List<String> DIRECTIONS = Arrays.asList("UP","DOWN","RIGHT","LEFT");

public static Optional<String> getDirectionPrefix(String input) {
    return DIRECTIONS.stream().filter(d -> input.startsWith(d)).findFirst();
}