Junit + String/Integer/ArrayList/HashMap/TreeMap 基本使用Demo

package JavaTest.test;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.TreeMap;
import org.junit.Test;

public class JavaBase {

    //@Test
    public void stringTest(){
        int i=0;
        String str=i+"";
        System.out.println(str.getClass());

        Integer num = Integer.valueOf(str);
        num++;
        System.out.println(num.getClass());

        String totalSize =null;
        System.out.println(stringToNumber(totalSize));

    }

    public int stringToNumber(String str){
        //参数字符串，先判断为空或者为null的情况，否则会报错
        if(str!=null&&!str.equals("")){
        return Integer.valueOf(str);
        }
        return 0;
    }

    //@Test
    public void arrayTest(){
        int[][] data1 = new int[][]{{1}};
        Object[][] data2=new Integer[][]{{1,2},{3,4}};
        Integer[][] data3 = new Integer[][]{{1,2,3},{4,5}};
        Integer[][] data4 = new Integer[5][5];
        for(int i=0,max=data3.length;i<max;i++){
            for(int j=0,max2=data3[i].length;j<max2;j++){
                //System.out.println(data3[i][j]);
            }
        }

        int t=0;
        for(int i=0;i<5;i++)
        {
            for(int j=0;j<5;j++){
                data4[i][j]=t++;
            }
        }
        for(Integer[] row:data4){
            for(Integer data:row){
                System.out.print(data+"\t");
            }
            System.out.println();
        }
    }

    //@Test
    public void arraylistTest(){
        List datalist = new ArrayList();
        datalist.add(1);
        datalist.add("2");
        datalist.add(true);
        datalist.add(new User());
        for(int i=0;i<datalist.size();i++){
            System.out.println(datalist.get(i));
        }

        List<Integer> dataList2 = new ArrayList<Integer>();
        dataList2.add(1);
        for(Integer i:dataList2){
            System.out.println(i);
        }
    }

    class User{
        private Integer UserID;

        private String UserName;

        public User() {

        }

        public User(int i, String string) {
             this.UserID=i;
             this.UserName=string;
        }
        public Integer getUserID() {
            return UserID;
        }
        public void setUserID(Integer userID) {
            UserID = userID;
        }
        public String getUserName() {
            return UserName;
        }
        public void setUserName(String userName) {
            UserName = userName;
        }
    }

    //@Test
    public void stringTest1(){
        String str1="testfan";
        String str2="tESTfAN";
        String str3=null;

        System.out.println(str2.equals(str1));
        System.out.println(str1.equalsIgnoreCase(str2));

        //不确定字符串是否为null,需要先于null进行比较
        if(str2!=null&&str2.trim().equals(str1)){
            System.out.println("str2 equal str1");
        }

        if("".equals(str3)){
            System.out.println("str 3 is blank");
        }

        //下面这种情况会报空指针异常，一般把比较对象放在后面，如上面
        if(str3.equals("")){
            System.out.println("str 3 is blank");
        }
    }

    //@Test
    public void equalsTest(){
        int num1=1;
        Integer num2 =2;
        if(num2.equals(num1)){
            System.out.println("equals");
        }

        //num1.equals(num2) 这样写是错的，只有对象才有方法，一个数字是没有方法的

        System.out.println(num2.equals(1));//如果数据类型不同，是没有意义的，永远为false
    }

    @Test
    public void mapTest(){
        Map usermap = new HashMap();
        usermap.put(1,new User(1,"testfan"));
        usermap.put(2, new User(2,"AryaZ"));
        usermap.put(3, "hello");
//        User user = (User)usermap.get(1);
//        System.out.println(user.getUserName());
//
        for(Object key:usermap.keySet()){
            Object value = usermap.get(key);
            if (value instanceof User) {
                User u= (User)value;
                System.out.println(u.getUserName());
            }else {
                System.out.println(value);
            }
        }

//-----------------------------hash map key无序,如果key是字符串，可以用treemap 排序
        Map<Integer, User> usermap2 = new HashMap<Integer, JavaBase.User>();
        usermap2.put(1,new User(1,"testfan2"));
        usermap2.put(2, new User(2,"AryaZ2"));
        System.out.println(usermap2.get(1).getUserName());

        for(Map.Entry<Integer, User> entry : usermap2.entrySet()){
            System.out.println(entry.getKey()+"  "+entry.getValue().getUserName());
        }
//-----------------------------    tree map ,会按照key的字典书序进行升序

        TreeMap sortedPara = new TreeMap();
        sortedPara.put("device_token", "123456");
        sortedPara.put("mobile", "187012345678");
        sortedPara.put("version", "app_ios_1.1");
        sortedPara.put("pass", "22222");

        //遍历排序后的字典，将所有参数按“key=value”格式拼接
        //stringBuild 来拼接字符串
        StringBuilder accum = new StringBuilder();
        for(Object key:sortedPara.keySet()){
            accum.append(key).append("=").append(sortedPara.get(key));
        }
        System.out.println(accum);
    }
}