content: package com.alibaba.qlexpress4.runtime.instruction;
  
  import com.alibaba.qlexpress4.QLOptions;
  import com.alibaba.qlexpress4.exception.ErrorReporter;
  import com.alibaba.qlexpress4.runtime.Parameters;
  import com.alibaba.qlexpress4.runtime.QContext;
  import com.alibaba.qlexpress4.runtime.QResult;
  import com.alibaba.qlexpress4.runtime.data.DataValue;
  import com.alibaba.qlexpress4.utils.PrintlnUtils;
  
  import java.util.function.Consumer;
  
  /**
   * Operation: concat n string on the top of stack
   * Input: ${n}
   * Output: concat result
   *
   * Author: DQinYuan
   */
  public class StringJoinInstruction extends QLInstruction {
      
      private final int n;
      
      public StringJoinInstruction(ErrorReporter errorReporter, int n) {
          super(errorReporter);
          this.n = n;
      }
      
      @Override
      public QResult execute(QContext qContext, QLOptions qlOptions) {
          Parameters arguments = qContext.pop(n);
          StringBuilder sb = new StringBuilder();
          for (int i = 0; i < n; i++) {
              sb.append(arguments.get(i).get());
          }
          qContext.push(new DataValue(sb.toString()));
          return QResult.NEXT_INSTRUCTION;
      }
      
      public int getN() {
          return n;
      }
      
      @Override
      public int stackInput() {
          return n;
      }
      
      @Override
      public int stackOutput() {
          return 1;
      }
      
      @Override
      public void println(int index, int depth, Consumer<String> debug) {
          PrintlnUtils.printlnByCurDepth(depth, index + ": StringJoin " + n, debug);
      }
  }
  