java常用数据结构常用方法-蒲公英云

java常用数据结构常用方法

String/StringBuffer/ArrayList本质一样，底层都为数组，只不过动态静态的区别，方法也基本类似

1.String

package com.ming.huawei;
public class TestString {
    public static void main(String[] args) {
        String a = " hello,paul234 ";
        String b = " 你好啊 2 123";
        String c = a.substring(2);
        System.out.println(c);
        String dString = a.substring(0, 3);
        System.out.println(dString);
        String eString = a.concat(b);
        System.out.println(eString);
        String fString = a.replace("e", "a");
        System.out.println(fString);
        int gString = a.indexOf("l");
        System.out.println(gString);
        String string = b.replaceAll("\\d", "d");
        System.out.println(string);
        System.out.println(a.charAt(2));
        System.out.println(b.contains("e"));
        char [] ds = a.toCharArray();
        a.isEmpty();
        a.indexOf("p");
        a.lastIndexOf("l");
        a.
    }
}

ello,paul234
he
hello,paul234 你好啊 2 123
hallo,paul234
3
你好啊 d ddd
e
false

2.StringBuffer

public class TestStringBuffer {
    public static void main(String[] args) {
        String str = "hello, 12345";
        StringBuffer sBuffer  = new StringBuffer(str);
        sBuffer.append("678");
        sBuffer.charAt(3);
        int start=0;
        int end=1;
        sBuffer.delete(start, end);
        sBuffer.deleteCharAt(3);
        sBuffer.indexOf("l");
        sBuffer.lastIndexOf("l");
        int fromIndex=0;
        sBuffer.indexOf(str, fromIndex);
        sBuffer.replace(start, end, str);
        sBuffer.reverse();
        sBuffer.substring(1);
        sBuffer.toString();
        String str1 = " 12345 ";
        StringBuffer sBuffer1  = new StringBuffer(str1);
        System.out.println(sBuffer1.length());
    }
}

3.HashMap

package com.ming.huawei;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.Map;
import java.util.Map.Entry;
import java.util.TreeMap;
public class TestHashMap {
    public static void main(String[] args) {
        Map<String, Integer> map = new HashMap<String, Integer>();
        Map<String, Integer> map1 = new TreeMap<String, Integer>();
        LinkedList<Integer> sIntegers = new LinkedList<Integer>();
        sIntegers.add(1);
        sIntegers.add(10200);
        sIntegers.add(6);
        sIntegers.add(78);
        sIntegers.sort(null);
        Object[] a = sIntegers.toArray();
        for(Object o:a){
            System.out.print(o);
        }
        map.put("1", 3);
        map.put("3", 3);
        map.put("2", 5);
        map.put("4", 2);
       Iterator iterator = map.entrySet().iterator();
       while(iterator.hasNext()){
           Map.Entry<String, Integer> sEntry = (Entry<String, Integer>) iterator.next();
           System.out.println(sEntry.getKey()+""+sEntry.getValue());
       }
    }
}

3.ArrayList(可排序，正，逆序)—可传入数据—数组—-string等

package com.ming.huawei;
import java.util.*;
public class TSort{
    public static void main(String[]args){
        Scanner scan=new Scanner(System.in);
        ArrayList<String> list=new ArrayList<String>();
        int num=scan.hasNextLine()?Integer.parseInt(scan.nextLine()):0;
        while(--num>=0&&scan.hasNextLine()){
             list.add(scan.nextLine());
        }
        Collections.sort(list);
//        for(String str:set){
//            System.out.println(str);
//        }
        System.out.println("升序: ");
        for(int i = 0;i < list.size(); i ++){
            System.out.print(" "+list.get(i));
        }
         System.out.println();
         System.out.println("降序: ");
        for(int i = list.size()-1;i >=0; i--){
            System.out.print(" "+list.get(i));
        }
    }
}

6
a
c
b
f
z
a
升序:
a a b c f z
降序:
z f c b a a

自定义排序：

Collections.sort(imageList, new Comparator() { 
public int compare(Object a, Object b) { 
int orderA = Integer.parseInt( ( (Image) a).getSequence()); 
int orderB = Integer.parseInt( ( (Image) b).getSequence()); 
return orderA - orderB; 
} 
});