编写Sonar规则检查代码中是否存在死循环，可以使用Sonar提供的Java AST Visitor模块。这个模块可以解析代码的抽象语法树，并可以检查代码中的每个元素。以下是一个示例代码，用于检查代码中是否有无限循环：

package org.sonar.samples.java.checks;

import org.sonar.check.Rule;
import org.sonar.check.Priority;
import org.sonar.check.RuleProperty;
import org.sonar.plugins.java.api.JavaFileScannerContext;
import org.sonar.plugins.java.api.JavaVersion;
import org.sonar.plugins.java.api.JavaVersionImpl;
import org.sonar.plugins.java.api.semantic.Symbol;
import org.sonar.plugins.java.api.semantic.Type;
import org.sonar.plugins.java.api.tree.*;
import org.sonar.plugins.java.api.tree.Tree.Kind;
import org.sonar.plugins.java.api.tree.TreeVisitorContext;
import org.sonar.plugins.java.api.tree.VariableTree;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

@Rule(
    key = "LoopShouldHaveExitCriteria",
    name = "Loop should have an exit criteria",
    description = "All loops should have an exit criteria to prevent infinite loops.",
    priority = Priority.CRITICAL,
    tags = {"bug"})
public class LoopShouldHaveExitCriteria extends BaseTreeVisitor {

  private List loopIndices = new ArrayList<>();

  @Override
  public void visitWhileStatement(WhileStatementTree tree) {
    checkLoop(tree, tree.condition());
    super.visitWhileStatement(tree);
  }

  @Override
  public void visitDoWhileStatement(DoWhileStatementTree tree) {
    checkLoop(tree, tree.condition());
    super.visitDoWhileStatement(tree);
  }

  @Override
  public void visitForStatement(ForStatementTree tree) {
    if (tree.condition() != null) {
      checkLoop(tree, tree.condition());
    }
    super.visitForStatement(tree);
  }

  private void checkLoop(StatementTree tree, ExpressionTree condition) {
    if (!condition.is(Kind.BOOLEAN_LITERAL) && !referencesLoopIndices(condition)) {
      context().newIssue(this, tree, "Add an exit criteria to this loop.");
    }
  }