java根据key或value对Map进行排序

迈不过友情╰ 2023-01-15 13:22 93阅读 0赞

## 根据key排序 ##

java.util包下的TreeMap可以满足此类需求，直接调用TreeMap的构造函数传入我们自己定义的比较器即可

public static Map<String, String> sortMapByKey(Map<String, String> map) {
        
    	if (map == null || map.isEmpty()) {
        
        	return null;
        }
    
    	Map<String, String> sortMap = new TreeMap<String, String>(
        	new Comparator<String>() {
        
            	@Override
                public int compare(String o1, String o2) {
        
                	return o1.compareTo(o2);
                }});
        sortMap.putAll(map);
    	return sortMap;
        }
    }

## 根据value排序 ##

原理：将map中所有的entry元素放在list容器中，调用Collections里的静态方法sort(List list, Comparator<? super T> c) 进行排序，重新compare方法定义排序规则。为了保证Map中元素与排序后的List中的元素的顺序一致，使用了LinkedHashMap。

public static Map<String, ExportExcelColumn> sortMapByValue(Map<String, ExportExcelColumn> oriMap) {
        
            if (oriMap == null || oriMap.isEmpty()) {
        
                return null;
            }
            Map<String, ExportExcelColumn> sortedMap = new LinkedHashMap<String, ExportExcelColumn>();
            List<Map.Entry<String, ExportExcelColumn>> entryList = new ArrayList<Map.Entry<String, ExportExcelColumn>>(oriMap.entrySet());
            Collections.sort(entryList, new Comparator<Entry<String, ExportExcelColumn>>() {
        
                @Override
                public int compare(Entry<String, ExportExcelColumn> o1, Entry<String, ExportExcelColumn> o2) {
        
    
                    return o1.getValue().getColumnSortNum() - o2.getValue().getColumnSortNum();
                }
            });
    
            Iterator<Map.Entry<String, ExportExcelColumn>> iter = entryList.iterator();
            Entry<String, ExportExcelColumn> tmpEntry = null;
            while (iter.hasNext()) {
        
                tmpEntry = iter.next();
                sortedMap.put(tmpEntry.getKey(), tmpEntry.getValue());
            }
            return sortedMap;
        }

ExportExcelColum类

public class ExportExcelColumn {
        
    
        private String columnName;
    
        private Integer columnSortNum;
        public ExportExcelColumn() {
        
    
        }
        public String getColumnName() {
        
            return columnName;
        }
        public void setColumnName(String columnName) {
        
            this.columnName = columnName;
        }
        public Integer getColumnSortNum() {
        
            return columnSortNum;
        }
        public void setColumnSortNum(Integer columnSortNum) {
        
            this.columnSortNum = columnSortNum;
        }
        public ExportExcelColumn(String columnName, Integer columnSortNum) {
        
            this.columnName = columnName;
            this.columnSortNum = columnSortNum;
        }
    }