前言

很多Java算法中都需要用到排序秒梅，但是往往在項目開發(fā)中并不需要自己實現(xiàn)排序功能怕敬，所以必須要熟練使用排序的庫函數(shù)才能快速的開發(fā)出高質(zhì)量的代碼置森。這篇博客就記錄以下常用的數(shù)組排序以及List排序，還有用處非常大的自定義對象數(shù)組排序

常見數(shù)據(jù)類型數(shù)組排序（正向）

Arrays.sort()

int []x = {3,8,3,2,4,1,4,1,2,2,6,5,5,3,5,1,0,2,4,2,0,4,8,4,2,1,9,4,3,9,6};
Arrays.sort(x);
for(int i =0;i<x.length;i++){
    System.out.print(x[i]);
}

  ##輸出結(jié)果
  0011112222223333444444555668899

一般對象數(shù)組（String槽卫、Integer拿诸、Character）正向與逆向排序

Arrays.sort(Object[] obj)升序
Arrays.sort(Object[] obj , Comparator.reverseOrder())降序

Java里面并沒有給int等自定義數(shù)據(jù)類型進行降序排列的函數(shù)

        String []strings = {"1","x","3","g","5","6","7"};
        Arrays.sort(strings,Comparator.reverseOrder());
        for(int i = 0;i<strings.length;i++){
            System.out.print(strings[i]);
        }

      ###輸出
      xg76531

自定義對象數(shù)組排序

方法一：實現(xiàn)Comparable接口的compareTo(Object o)扒袖，然后調(diào)用函數(shù)自動按照規(guī)則排序。

class Name implements Comparable<Name>{
    public String firstName;
    public String lastName;
    public Name(String first,String last){
        this.firstName = first;
        this.lastName = last;
    }
    @Override
    public int compareTo(Name o) {
        int lastCmp = firstName.compareTo(o.firstName);
        return(!(lastCmp==0)?lastCmp:lastName.compareTo(o.lastName));
    }
    public String toString(){
        return firstName + " " + lastName;
    }
}

##############    測試
Name names[] ={new Name("John","Muhaha"),new Name("Gao","Dev"),new Name("Susan","JInjiao")};
        Arrays.sort(names);
        for(int i = 0 ;i<names.length;i++){
            System.out.println(names[i].toString());
        }
################    輸出
Gao Dev
John Muhaha
Susan JInjiao

方法二：自定義比較參數(shù)亩码，在排序時傳入新創(chuàng)建的比較參數(shù)實現(xiàn)比較效果(實現(xiàn)compare(Object o1,Object o2))）

******自定義類********
class Name2{
    public String firstName;
    public String lastName;
    public Name2(String first,String last){
        this.firstName = first;
        this.lastName = last;
    }
    public String toString(){
        return firstName + " " + lastName;
    }
}

*******創(chuàng)建排序參數(shù)********
Comparator<Name2> comparator = new Comparator<Name2>() {
            @Override
            public int compare(Name2 o1, Name2 o2) {
                int bigger = o1.firstName.compareTo(o2.firstName);
                return (!(bigger==0)?bigger:o1.lastName.compareTo(o2.lastName));
            }
        };
******測試************
Arrays.sort(names2,comparator);
        for(int i = 0 ;i<names2.length;i++){
            System.out.println(names2[i].toString());
        }
******輸出************
Wang Dev
Xing JInjiao
Yao Muhaha