java - 检查数组中的字符串是否以开头开头

Question

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

有没有一种方法可以检查输入字符串是否开始方向上有一个值不使用分割输入值？

Answer 1

当然 - 只需迭代所有方向即可:

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();
}