Android-Collections.sort()

逃离我推掉我的手 2023-01-17 12:52 100阅读 0赞

将对象进行比较  
但是对象中有多种属性  
方法一：

public class FriendInfo implements Comparable<Student> { 
        private String name;
        private String pinyin;
        private String firstLetter;
    
        public String getFirstLetter() { 
            return firstLetter;
        }
    
        public void setFirstLetter(String firstLetter) { 
            this.firstLetter = firstLetter;
        }
    
        public FriendInfo() { 
        }
    
        public String getName() { 
            return name;
        }
    
        public void setName(String name) { 
            this.name = name;
        }
    
        public String getPinyin() { 
            return pinyin;
        }
    
        public void setPinyin(String pinyin) { 
            this.pinyin = pinyin;
        }
        
    	@Override
        public int compareTo(FriendInfoom f) { 
            //通过首字符比较进行升序排序
            return this.firstLetter - f.firstLetter;
        }
        
        @Override
        public String toString() { 
            return "FriendEntity{" +
                    "name='" + name + '\'' +
                    ", pinyin='" + pinyin + '\'' +
                    '}';
        }
    
    }
    
    }
    
    
    /** * 测试代码 */
    Collections.sort(list);

实现Comparable可以使对象可比较的  
方法二：

Collections.sort(friends, new Comparator<FriendInfo>() { 
                @Override
                public int compare(FriendInfo f1, FriendInfo f2) { 
                    if (f1.getFirstLetter().contains("#")) { 
                        return 1;
                    } else if (f2.getFirstLetter().contains("#")) { 
                        return -1;
                    }
                    else{ 
                        return f1.getFirstLetter().compareTo(f2.getFirstLetter());
    
                    }
                }
            });

但是在jdk1.7版本以上，需要添加一条比对二者相等的情况，返回0，否则会报错  
java.lang.IllegalArgumentException: Comparison method violates its general contract!