Set接口 (2)

按照名字进行比较，如果名字相同，在compareTo中比较返回值为0（TreeSet中判断是否相同的标准不再是equals，而是compareTo）

//姓名从小到大排列，姓名相同的年龄从小到大排列 @Override public int compareTo(Object o) { if(o instanceof Students){ Students s = (Students)o; // return this.name.compareTo(s.name); int compare = this.name.compareTo(s.name); //姓名不一样 if(compare != 0){ return compare; }else { //姓名一样 return Integer.compare(this.age,s.age); } }else{ throw new RuntimeException("传入数据类型不一致"); } @Test public void test13(){ TreeSet set = new TreeSet(); set.add(new Students("Tom",18,90)); set.add(new Students("Ann",19,75)); set.add(new Students("Lisa",20,86)); set.add(new Students("Jack",21,50)); set.add(new Students("Jerry",19,60)); set.add(new Students("Jerry",22,70)); Iterator iterator = set.iterator(); while (iterator.hasNext()){ System.out.println(iterator.next()); } }

运行结果

定制排序（实现Comparator接口）

在定制排序中，比较两个对象是否相同的标准为compare()，是否返回0，不再是equals()方法

TreeSet set = new TreeSet();

构造器没有参数的时候直接为自然排序

TreeSet set = new TreeSet(com);

构造器有蚕食的时候，按照com的定制排序进行排序

代码实现

普通情况，按照年龄进行排序

//年龄从小到大进行排序 public void test14(){ Comparator com = new Comparator() { //按照年龄从小到大排列 @Override public int compare(Object o1, Object o2) { if(o1 instanceof Students || o2 instanceof Students){ Students s1 = (Students)o1; Students s2 = (Students)o2; return Integer.compare(s1.getAge(),s2.getAge()); }else{ throw new RuntimeException("传入数据类型不一致"); } } }; TreeSet set = new TreeSet(com); set.add(new Students("Tom",18,90)); set.add(new Students("Ann",19,75)); set.add(new Students("Lisa",20,86)); set.add(new Students("Jack",21,50)); set.add(new Students("Jerry",19,60)); set.add(new Students("Jerry",22,70)); Iterator iterator = set.iterator(); while (iterator.hasNext()){ System.out.println(iterator.next()); } }

运行结果

排序的信息有相同的情况（年龄相同，其他信息不相同）

public void test14(){ Comparator com = new Comparator() { //按照年龄从小到大排列 @Override public int compare(Object o1, Object o2) { if(o1 instanceof Students || o2 instanceof Students){ Students s1 = (Students)o1; Students s2 = (Students)o2; // return Integer.compare(s1.getAge(),s2.getAge()); int compare = Integer.compare(s1.getAge(), s2.getAge()); if(compare != 0){ return Integer.compare(s1.getAge(),s2.getAge()); }else{ return s1.getName().compareTo(s2.getName()); } }else{ throw new RuntimeException("传入数据类型不一致"); } } }; TreeSet set = new TreeSet(com); set.add(new Students("Tom",18,90)); set.add(new Students("Ann",19,75)); set.add(new Students("Lisa",20,86)); set.add(new Students("Jack",21,50)); set.add(new Students("Jerry",19,60)); set.add(new Students("Jerry",22,70)); Iterator iterator = set.iterator(); while (iterator.hasNext()){ System.out.println(iterator.next()); } }

运行截图