Appending with StringBuilder

问题

I have 5 checkboxes and I have to select multiple checkboxes.

I made a code like this to check check box is checked:

sports=(CheckBox)findViewById(R.id.sports_btn);
sports.setOnClickListener(new OnClickListener() {

    @Override
    public void onClick(View v) {
        if (sports.isChecked() == true)
        list.add("4");
    }
});

I am adding a value to an array list:

list ArrayList<String> list = new ArrayList<String>();

and I am retrieving the value as string like this:

StringBuilder sb = new StringBuilder();
for(int  i =0; i < list.size(); i++)
{
    for (String str: list)
    {  
        sb.append(str.toString());
        sb.append(",");
    }

}
String sel_cat = sb;

I am getting the string but if two values are selected it is coming like 2,3, How to remove that last comma? I don't want the last comma the string has to be like 2,3.

回答1:

StringBuilder sb = new StringBuilder();
sb.deleteCharAt(sb.length()-1)

Or in your code, use

StringBuilder sb = new StringBuilder();

for(int  i =0;i<list.size();i++)
{
    String prefix = "";
    for (String str : list)
    { 
        sb.append(prefix);
        prefix = ",";
        sb.append(str);  
    }
}

String sel_cat = sb;

回答2:

You can put the condition to check:

for (String str : list)
{
   sb.append(str.toString());
   if (i!=list.size()-1)
   {
     sb.append(",");
   }
}

回答3:

You can put your string array in condition:

String list[]=new String[]{"A","C","D","F"};

public String print(String arr[]){

    StringBuilder sb = new StringBuilder();
    String prefix = "";
    for (String str : arr)
    { 
        sb.append(prefix);
        prefix = ",";
        sb.append(str);  
    }

    System.out.println("WithCommas"+sb);
    return sb;
}

回答4:

You can use deleteCharAt:

StringBuilder sb = new StringBuilder();
for(int  i =0;i<list.size();i++)
{
    for (String str : list)
    {  
        sb.append(str); // str is already a String, no need for toString()
        sb.append(",");
    }
}
if (sb.length() > 0) {
    sb.deleteCharAt(sb.length()-1);
}
String sel_cat=sb;

回答5:

Another option is to look at StringUtils#join(Object\[\], String, int, int):

there is a join method which can take an array and put it together with a delimeter...

ex:

 StringUtils.join([null, "", "a"], ',')   // creates... ",,a"

回答6:

import android.app.DatePickerDialog;
import android.app.TimePickerDialog;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.DatePicker;
import android.widget.EditText;
import android.widget.ImageButton;
import android.widget.ScrollView;
import android.widget.TimePicker;

来源：https://stackoverflow.com/questions/8167088/appending-with-stringbuilder

标签

android

checkbox

stringbuilder