Java 将循环结果另存为字符串

如何操作？

使用a将字符串连接在一起。（从技术上讲，可以使用字符串对象，并使用+运算符将它们连接在一起，但这有很多缺点…）

---

您不断将其附加到

StringBuilder

中，然后将其转换为

String

public abstract class MyQueryBuilder {

    protected abstract void addFields(StringBuilder sb);
    protected abstract void addFromPart(StringBuilder sb);
    protected abstract void addWhereClause(StringBuilder sb);

    public final String getQuery() {
        StringBuilder sb = new StringBuilder();
        sb.append("SELECT ");

        addFields(sb); //this adds the fields to be selected
        sb.append(" FROM ");

        addFromPart(sb); //this adds the tables in the FROM clause

        addWhereClause(sb); //this adds the where clause
        //...etc
        return sb.toString();
    }
}

---

您可以使用StringBuilder来执行此操作，而不是打印值

String query = "select "+sb.toString()+" from table";

String input[]=request.getParameterValues（“复选框”）；
StringBuilder=新的StringBuilder（）；
对于（int i=0；iVery good，它可以工作。我使用查询字符串，最后使用：request.getRequestDispatcher（“/response.jsp”）.forward（request，response）；在这个jsp上，我现在想使用JasperReports将显示的表导出为PDF。在IReport设计中，将结果字符串用作查询的参数是行不通的。
    String input[] = request.getParameterValues("checkbox");

    StringBuilder sb = new StringBuilder(); // create empty StringBuilder instance
    for(int i=0;i<input.length;i++) {
        sb.append(input[i]);     //append element
        if (i==input.length-1) {
            sb.append(" ");      //append space
        } else {
            sb.append(", ");     //append comma
        }
    }

    String result = sb.toString();
    Systemout.println(result);

public abstract class MyQueryBuilder {

    protected abstract void addFields(StringBuilder sb);
    protected abstract void addFromPart(StringBuilder sb);
    protected abstract void addWhereClause(StringBuilder sb);

    public final String getQuery() {
        StringBuilder sb = new StringBuilder();
        sb.append("SELECT ");

        addFields(sb); //this adds the fields to be selected
        sb.append(" FROM ");

        addFromPart(sb); //this adds the tables in the FROM clause

        addWhereClause(sb); //this adds the where clause
        //...etc
        return sb.toString();
    }
}

StringBuilder sb = new StringBuilder();
for(int i=0;i<input.length;i++) {
  if (i==input.length-1) {
     System.out.print(input[i]+" ");
     sb = sb.concat(input[i] + ",");
  } else {
     System.out.print(input[i]+", ");
     sb = sb.concat(input[i] + ",");
  }
}

String query = "select "+sb.toString()+" from table";

String input[] = request.getParameterValues("checkbox");

    StringBuilder builder = new StringBuilder();

    for(int i=0;i<input.length;i++) {
        if (i==input.length-1) {
            builder.append(input[i]+" ");
        } else {
                builder.append(input[i]+", ");
        }
    }