1、集合泛型 参数设置两种方式：

public void setData(ArrayList
     data)	{		mNavigatorAdapter.setData(data);	}	public 
    
      void setData(ArrayList
     
       data)	{		mNavigatorAdapter.setData(data);	}
     
    

2、map排序

Comparator mComparator =  new Comparator
    
     () {            public int compare(String str1, String str2) {                return str1.compareTo(str2);            }        };                Map
     
       sortMap = new TreeMap<>(mComparator);        if(params != null){            sortMap.putAll(params);        }        StringBuilder sb = new StringBuilder();        for (Map.Entry
      
        entry : sortMap.entrySet()) {            sb.append(entry.getValue());        }
      
     
    

3、单例

publlic class Singleton {    private Singleton() {}    private static class SingletonLoader {        private static final Singleton INSTANCE = new Singleton();    }     public static Singleton getInstance() {        return SingletonLoader.INSTANCE;    }}//这种方式可以给构造函数传参public class Singleton {    private volatile static Singleton instance; //声明成 volatile    private Singleton (){}    public static Singleton getSingleton() {        if (instance == null) {                                     synchronized (Singleton.class) {                if (instance == null) {                           instance = new Singleton();                }            }        }        return instance;    }   }

4、重写equals方法，可以比较两个不同对象的是否相等，可以用于ArrayList排重