Flat2Nest.java

public class Flat2Nest {
    public static void main(String[] args) {
        String testProp = "java.class.version = 60.0\n" +
                "java.home = /usr/lib/jvm/java-16-openjdk\n" +
                "java.runtime.name = OpenJDK Runtime Environment\n" +
                "java.runtime.version = 16.0.2+7\n" +
                "java.specification.name = Java Platform API Specification\n" +
                "java.specification.vendor = Oracle Corporation\n" +
                "java.specification.version = 16\n" +
                "java.vendor = N/A\n" +
                "java.vendor.url = https://openjdk.java.net/\n" +
                "java.vendor.url.bug = https://bugreport.java.com/bugreport/\n" +
                "java.version = 16.0.2\n" +
                "java.version.date = 2021-07-20\n" +
                "java.vm.name = OpenJDK 64-Bit Server VM\n" +
                "java.vm.specification.name = Java Virtual Machine Specification\n" +
                "java.vm.specification.vendor = Oracle Corporation\n" +
                "java.vm.specification.version = 16\n" +
                "java.vm.vendor = Oracle Corporation\n" +
                "java.vm.version = 16.0.2+7\n" +
                "sun.arch.data.model = 64";
        Map<String, Object> initMap = Arrays.stream(testProp.split("\n"))
                .map(it -> {
                    int i = it.indexOf("=");
                    return new AbstractMap.SimpleEntry<>(
                            it.substring(0, i).trim(),
                            it.substring(i + 1).trim());
                })
                .collect(Collectors.toMap(
                        AbstractMap.SimpleEntry::getKey,
                        AbstractMap.SimpleEntry::getValue)
                );
        System.out.println(initMap);
        Map<String, Object> finalMap = nestMap(initMap);
        System.out.println(finalMap);

    }

    public static Map<String, Object> nestMap(Map<String, Object> map) {
        Set<String> keys = new HashSet<>();
        keys.addAll(map.keySet());
        int size = 1;
        String flag = null;
        /*第一次遍历，取出最深层次的key*/
        for (String s : keys) {
            /*两次转义*/
            String[] temp = s.split("\\.");
            int dotNum = temp.length;
            if (size < dotNum) {
                size = dotNum;
                flag = s.substring(0, s.lastIndexOf("."));
            }
        }
        /*递归跳出*/
        if (flag == null) {
            return map;
        }
        Map<String, Object> subMap = new HashMap<>();
        /*第二次遍历，将最深层次变为map*/
        for (String v : keys) {
            if (v.startsWith(flag)) {
                if (v.length() > flag.length()) {
                    subMap.put(v.substring(flag.length() + 1), map.get(v));
                } else {
                    subMap.put(flag, map.get(v));
                }
                map.remove(v);
            }
        }
        /*将最深层次map放入*/
        map.put(flag, subMap);
        /*递归*/
        return nestMap(map);
    }
}