Guava 工具类之joiner的使用

public class JoinerTest {
    
    private static final List<String> list1 = Arrays.asList
                ("google","guava","java","scala","kafka");
    
    private static final List<String> list2 = Arrays.asList
            ("google","guava","java",null,"scala","kafka");
    
    public static void main(String[] args) throws IOException {
        
        //1.用指定的字符连接
        String join = Joiner.on("#").join(list1);
        System.out.println("用 # 号连接的字符串是："+join);
        
        //2.跳过连接中的null值
        String joinNull = Joiner.on("#").skipNulls().join(list2);
        System.out.println("用 # 号连接的字符串,跳过中间的null值："+joinNull);
        
        //3.有null值存在时用指定值代替
        String joinUseForNull = Joiner.on("#").useForNull("DEFAULT").join(list2);
        System.out.println("用指定值代替集合中的null值："+joinUseForNull);
        
        //4.把集合变成一个stringBuilder 或者stringBuffer
        StringBuilder builder = Joiner.on("#").useForNull("DEFAULT").appendTo(new StringBuilder(), list2);
        StringBuffer buffer = Joiner.on("#").useForNull("DEFAULT").appendTo(new StringBuffer(), list2);
        System.out.println("拼接成的 builder是："+builder);
        System.out.println("拼接成的buffer是："+buffer);
        
        //5.对于key value的分隔
        Map<String, String> map = new HashMap<String, String>();
        map.put("hello", "java");
        map.put("scala", "guava");
        String joinMap = Joiner.on("#").withKeyValueSeparator("=").join(map);
        System.out.println("key value 的分隔符："+joinMap);
        
    }
}