各种类型转换全家桶这(一篇就够了)
String转int (int转String):
String转int :
String a="6666";
Integer a1 = Integer.parseInt(a); 或 int a1 = Integer.parseInt(a);
int转String :
int a=12;
String a1 = String.valueOf(a);
String a2 = a+"";
String转Long (Long转String)
String转Long :
String a = “6666”;
Long a = Long.valueOf(a) // 返回Long包装类型
long a1 = Long.parseLong(a) // 返回long基本数据类型
Long转String :
long a1 = 12;
String s1 = a1 + “”; // 法1:直接加空串
long a2 = 34;
String s2 = String.valueOf(a2); // 法2:String.valueOf()
long a3 = 56;
String s3 = Long.toString(a3); // 法3:Long.toString()
String转Double (Double转String)
String转Double :
注意转换精度问题 使用BigDecimal
String a=“6666000000”;
double aa=Double.parseDouble(a);
BigDecimal beichushu=new BigDecimal(aa);
BigDecimal chushu=new BigDecimal(100000000); //根据你想得到的是多大的数 来除以多少个0
BigDecimal result=beichushu.divide(chushu,new MathContext(4));//MathConText(4)表示结果精确4位!
// 2
String toBeDouble =“200.20”;
Double fromString = new Double(toBeDouble);
Double转String :
Double toBeString = 400.40;
String fromDouble = “” + toBeString;
String strDouble = String.valueOf(toBeString);
String stringDouble = toBeString.toString();
String convertedString = String.format(“%。3f”,toBeString);
String 转list
String[] strs = {“qq”,“ww”,“ee”};
List strsToList1= Arrays.asList(strs);
或
String[] strs = {“qq”,“ww”,“ee”};
List strsToList2=new ArrayList<>();
Collections.addAll(strsToList2,strs);
或
String[] strs = {“qq”,“ww”,“ee”};
List strsToList3=new ArrayList<>();
for(String s:strs){
strsToList3.add(s);
}
String 转map 以及 map转String
public class Test05 {
public static void main(String[] args) {
Map<String,Object> map = new HashMap<>(3);
map.put("name","小明");
map.put("sex","男");
map.put("age","16");
//Map转String
String str1 = getMapToString(map);
System.out.println(str1);
try {
//String转map
Map<String, Object> map1 = getStringToMap(str1);
System.out.println(map1);
} catch (Exception e) {
e.printStackTrace();
}
}
/**
*
* Map转String
* @param map
* @return
*/
public static String getMapToString(Map<String,Object> map){
Set<String> keySet = map.keySet();
//将set集合转换为数组
String[] keyArray = keySet.toArray(new String[keySet.size()]);
//给数组排序(升序)
Arrays.sort(keyArray);
//因为String拼接效率会很低的,所以转用StringBuilder
StringBuilder sb = new StringBuilder();
for (int i = 0; i < keyArray.length; i++) {
// 参数值为空,则不参与签名 这个方法trim()是去空格
if ((String.valueOf(map.get(keyArray[i]))).trim().length() > 0) {
sb.append(keyArray[i]).append(":").append(String.valueOf(map.get(keyArray[i])).trim());
}
if(i != keyArray.length-1){
sb.append(",");
}
}
return sb.toString();
}
/**
*
* String转map
* @param str
* @return
*/
public static Map<String,Object> getStringToMap(String str){
//根据逗号截取字符串数组
String[] str1 = str.split(",");
//创建Map对象
Map<String,Object> map = new HashMap<>();
//循环加入map集合
for (int i = 0; i < str1.length; i++) {
//根据":"截取字符串数组
String[] str2 = str1[i].split(":");
//str2[0]为KEY,str2[1]为值
map.put(str2[0],str2[1]);
}
return map;
}
}
本文地址:https://blog.csdn.net/nanZhaiXiaoLang/article/details/113929638
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