package computerPractice;

import java.util.Scanner;

public class StringSplicing {

	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);
		String str = "", splice = "";
		do {
			System.out.print("请输入一个字符串(输入000退出)：");
			str = sc.next();
			splice += str;
			if (str.equals("000")) {
				break;
			} else {
				System.out.println();
			}
		} while (!"000".equals(str));
		System.out.println("\n您输入的字符串的完整展示为：" + splice);

		sc.close();

	}

}

在java中，查询某工号下用户的权限值，拼接为字符串，返回
 
表中数据结构如下：
 
 
查询结果如下：
 
 
拼接permissionCode值；
 
代码如下：
List<UpsUserRoleMenu> roleMenus = upsUserRoleMapper.selectRoleAndSysId(userId);
		String roleId = null;
		Integer sysId =null;
		for (UpsUserRoleMenu upsUserRoleMenu : roleMenus) {
			roleId = upsUserRoleMenu.getRoleId();
			sysId = upsUserRoleMenu.getSysId();
			try {				
				List<UpsRolePermissionDataparams> menus_list = upsRolePermissionDataParamersMapper
						.selectByUserId(Integer.valueOf(roleId),sysId);
				StringBuffer permission = new StringBuffer();
				if(null != menus_list && menus_list.size() != 0){					
					for(int i=0;i<menus_list.size(); i++){
						UpsRolePermissionDataparams menu = menus_list.get(i);
						if(i == 0){
							permission.append(menu.getPermissionCode());
						}else{
							permission.append(","+menu.getPermissionCode());
						}
					}
					upsUserRoleMenu.setPermission(permission.toString());				
				}
			} catch (Exception e) {
				e.printStackTrace();
			}
		}

 
 结果如下图： 
 

public static void main(String[] args) {
    List<String> list = new ArrayList<>();
    list.add("assssssssss");
    list.add("bssssssssss");
    list.add("cssssssssss");
    list.add("dssssssssss");
    list.add("essssssssss");
    list.add("fssssssssss");
    list.add("gssssssssss");
    //在循环外面定义str
    String str = "";
    for (int i = 0; i < list.size(); i++) {
        //不断相加
        if (i != 0) {
            str += ",";
        }
        str += list.get(i);
    }
    //在循环外面取
    System.out.println(str);
}
 
展示：
 
 或者：
 
//list集合
List<info > bondRepoSubdataList = (List<info >) basedao.findByHql(" select * from info '");
                          StringBuffer resultBuffer = new StringBuffer();     
                           //for循环得到值
                            for (int m=0;m<bondRepoSubdataList.size();m++){
                                 bondNo=bondRepoSubdataList.get(m).getaaa();
                                if (m == 0) {
                                //只有一个值的时候输出
                                    resultBuffer.append(bondNo)；
                                }else{
                                //有多个值的时候分号分割
                                    resultBuffer.append("；" + bondNo);

                                }

                            }
                            //字符串拼接的结果集
                            String	testResult = resultBuffer.toString();
                            tempList.add(testResult == null ? "" : testResult);

public class StringBuilderTest {
    public String implicit(String[] fields) {
        String result = "";
        for(int i = 0; i < fields.length; i++)
            result += fields[i];
        return result;
    }
    public String explicit(String[] fields) {
        StringBuilder result = new StringBuilder();
        for(int i = 0; i < fields.length; i++)
            result.append(fields[i]);
        return result.toString();
    }
}
 
用jdk自带工具反编译以上代码：
 
 
implicit方法在循环体内用"+"拼接字符串，编译器会在循环体内自动new StringBuilder()；
 
 
explicit方法直接在循环体外new StringBuilder(),在循环体内用append追加，
 
//用一个容量为11409的string数组测试
String []filds = dpcq1.split("");
System.out.println(filds.length);
StringBuilderTest stringBuilderTest = new StringBuilderTest();

long implicitStart = System.currentTimeMillis();
stringBuilderTest.implicit(filds);
long implicitEnd = System.currentTimeMillis();
long implicitTime = implicitEnd-implicitStart;

long explicitStart = System.currentTimeMillis();
stringBuilderTest.explicit(filds);
long explicitEnd = System.currentTimeMillis();
long explicitTime = explicitEnd-explicitStart;

System.out.println("implicitStart ="+implicitStart);
System.out.println("implicitEnd ="+implicitEnd);
System.out.println("implicitTime ="+implicitTime);

System.out.println("explicitStart ="+explicitStart);
System.out.println("explicitEnd ="+explicitEnd);
System.out.println("explicitTime ="+explicitTime);
 
打印输出如下：
 
 
备注：以上在idea上用jdk1.8测试