[英]How to sort the arrays in ArrayList?
我有ArrayList,它包含許多數組,每個數組包含名字,姓氏。 現在我想根據姓氏對列表進行排序。
例:
ArrayList<String[]> list=new ArrayList<String[]>();
String[] name1={"koti" ,"reddy"};
String[] name2={"hanu" ,"sanjay"};
String[] name3={"ajay" ,"zedeja"};
String[] name4={"basha" ,"kadhar"};
list.add(name1);
list.add(name2);
list.add(name3);
list.add(name4);
我想要這樣的排序順序:
basha kadhar
koti reddy
hanu sanjay
ajay zedeja
請您盡快提供幫助,謝謝
編寫一個自定義的比較器,並將其與數據一起提供給適當的sort
重載。
但是,我建議使用單獨的Person/Name
類型而不是String數組,因為它可以使數據更容易跟蹤, 並且可以實現Comparable (這將消除/替換Comparator的需求)。
現在,在編寫適用的compare/compareTo
,代碼應類似於:
int cmpLastName = a_lastName.compareTo(b_lastName);
if (cmpLastName == 0) {
// same lastname, order now based on first name
return a_firstName.compareTo(b_firstName);
} else {
// different lastname, so have enough ordering
return cmpLastName;
}
嘗試這個
Collections.sort(list, new Comparator<String[]>() {
@Override
public int compare(String[] o1, String[] o2) {
int c = o1[0].compareTo(o2[0]);
if (c != 0) {
return c;
}
return o1[1].compareTo(o2[1]);
}
});
這就是我執行該排序操作的方式。
public static void main(String[] args) {
ArrayList<String[]> list = new ArrayList<String[]>();
String[] name1 = { "koti", "reddy" };
String[] name2 = { "hanu", "sanjay" };
String[] name3 = { "ajay", "zedeja" };
String[] name4 = { "basha", "kadhar" };
list.add(name1);
list.add(name2);
list.add(name3);
list.add(name4);
System.out.println("Before sorting");
for (String[] r : list) {
System.out.println(Arrays.toString(r));
}
Collections.sort(list, new Comparator<String[]>() {
public int compare(String[] left, String[] right) {
if (left == null) { // null?
if (right == null) { // null == null!
return 0;
}
return -1; // null < not(null)
} else if (right == null) {
return 1; // not(null) > null.
}
// If the last names aren't the same, return the result
// of comparing the last names.
if (left[1].compareTo(right[1]) != 0) {
return left[1].compareTo(right[1]);
}
// Return the result of comparing the first names.
return left[0].compareTo(right[0]);
}
});
System.out.println("After sorting");
for (String[] r : list) {
System.out.println(Arrays.toString(r));
}
}
嘗試使用此代碼來實現輸出。
public static void main(String []args){
ArrayList<String[]> list=new ArrayList<String[]>();
String[] name1={"koti" ,"reddy"};
String[] name2={"hanu" ,"sanjay"};
String[] name3={"ajay" ,"zedeja"};
String[] name4={"basha" ,"kadhar"};
list.add(name1);
list.add(name2);
list.add(name3);
list.add(name4);
Collections.sort(list, new Comparator<String[]>() {
@Override
public int compare(String[] s1, String[] s2) {
int i = s1[0].compareTo(s2[0]);
if (i != 0) {
return i;
}
return s1[1].compareTo(s2[1]);
}
});
System.out.println("after sorting"+"\n");
for (String[] s : list) {
for(int i=0;i<s.length;i++){
System.out.print(s[i]+"\t");
}
System.out.print("\n");
}
}
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